The samples/bluetooth/mesh fails on my nrf52840_pca10056

Below is the debug output of both the failing and non-failing cases.

I bisected down to:
first bad commit: [aaeff3c165051c15dfa025f1aad82f333395b6d0] 
Bluetooth: Add basic host-side support for HCI vendor extension

Somewhere CONFIG_BT_HCI_VS_EXT defaults to "y". If I set it to "n" in prj.conf, all is well.

Steve

====== failing log ============
Initializing...
[bt] [INF] hci_vs_init: HW Platform: Nordic Semiconductor (0x0002)
[bt] [INF] hci_vs_init: HW Variant: nRF52x (0x0002)
[bt] [INF] hci_vs_init: Firmware: Standard Bluetooth controller (0x00) Version 1.9 Build 99
[bt] [INF] show_dev_info: Identity: cf:f1:b8:81:59:d0 (random)
[bt] [INF] show_dev_info: HCI: version 5.0 (0x09) revision 0x0000, manufacturer 0xffff
[bt] [INF] show_dev_info: LMP: version 5.0 (0x09) subver 0xffff
Bluetooth initialized
[bt] [INF] bt_mesh_prov_init: Device UUID: 00000000-0000-0000-0000-cff1b88159d0
[bt] [DBG] bt_mesh_scan_enable: (0x20001bb8)
[bt] [DBG] adv_thread: (0x200007f8) started
[bt] [DBG] bt_mesh_proxy_adv_start: (0x200007f8)
[bt] [DBG] adv_thread: (0x200007f8) Proxy Advertising up to 60000 ms
[bt] [DBG] bt_mesh_proxy_prov_enable: (0x20001bb8)
Mesh initialized
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] bt_mesh_proxy_adv_stop: (0x200007f8) adv_enabled 1
[bt] [DBG] adv_send: (0x200007f8) type 2 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] adv_send: (0x200007f8) count 3 interval 20ms duration 90ms
[bt] [DBG] pub_key_ready: (0x20000370) Local public key ready
ecc stack (real size 1324): unused 448 usage 876 / 1324 (66 %)
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 23: 00d05981b8f1cf00000000000000000000000000000000
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] unprovisioned_beacon_send: (0x20001bb8)
[bt] [ERR] unprovisioned_beacon_send: Unable to allocate beacon buffer

======== successful log =============
adv stack (real size 812): unused 384 usage 428 / 812 (52 %)
Kernel stacks:
main (real size 512): unused 272 usage 240 / 512 (46 %)
idle (real size 320): unused 272 usage 48 / 320 (15 %)
interrupt (real size 2048): unused 1616 usage 432 / 2048 (21 %)
workqueue (real size 2048): unused 1704 usage 344 / 2048 (16 %)
[bt] [DBG] bt_mesh_proxy_adv_start: (0x200007f8)
[bt] [DBG] gatt_proxy_advertise: (0x200007f8)
[bt] [DBG] net_id_adv: (0x200007f8)
[bt] [DBG] net_id_adv: (0x200007f8) Advertising with NetId d47679433fdb104a
[bt] [ERR] net_id_adv: Failed to advertise using Network ID (err -5)
[bt] [DBG] adv_thread: (0x200007f8) Proxy Advertising up to -1 ms
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] secure_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_beacon_create: (0x20001bb8) net_idx 0x0000 flags 0x00 NetID d47679433fdb104a
[bt] [DBG] bt_mesh_beacon_create: (0x20001bb8) IV Index 0x00000005 Auth f40a41fab0af320b
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 22: 0100d47679433fdb104a00000005f40a41fab0af320b
[bt] [DBG] bt_mesh_proxy_adv_stop: (0x200007f8) adv_enabled 0
[bt] [DBG] adv_send: (0x200007f8) type 2 len 22: 0100d47679433fdb104a00000005f40a41fab0af320b
[bt] [DBG] adv_send: (0x200007f8) count 1 interval 20ms duration 30ms
[bt] [DBG] beacon_complete: (0x200007f8) err 0
[bt] [DBG] adv_send: (0x200007f8) Advertising started. Sleeping 30 ms
[bt] [DBG] adv_send: (0x200007f8) Advertising stopped
adv stack (real size 812): unused 384 usage 428 / 812 (52 %)
Kernel stacks:
main (real size 512): unused 272 usage 240 / 512 (46 %)
idle (real size 320): unused 272 usage 48 / 320 (15 %)
interrupt (real size 2048): unused 1616 usage 432 / 2048 (21 %)
workqueue (real size 2048): unused 1704 usage 344 / 2048 (16 %)
[bt] [DBG] bt_mesh_proxy_adv_start: (0x200007f8)
[bt] [DBG] gatt_proxy_advertise: (0x200007f8)
[bt] [DBG] net_id_adv: (0x200007f8)
[bt] [DBG] net_id_adv: (0x200007f8) Advertising with NetId d47679433fdb104a
[bt] [ERR] net_id_adv: Failed to advertise using Network ID (err -5)
[bt] [DBG] adv_thread: (0x200007f8) Proxy Advertising up to -1 ms
[bt] [DBG] beacon_send: (0x20001bb8)
[bt] [DBG] secure_beacon_send: (0x20001bb8)
[bt] [DBG] bt_mesh_beacon_create: (0x20001bb8) net_idx 0x0000 flags 0x00 NetID d47679433fdb104a
[bt] [DBG] bt_mesh_beacon_create: (0x20001bb8) IV Index 0x00000005 Auth f40a41fab0af320b
[bt] [DBG] bt_mesh_adv_send: (0x20001bb8) type 0x02 len 22: 0100d47679433fdb104a00000005f40a41fab0af320b
[bt] [DBG] bt_mesh_proxy_adv_stop: (0x200007f8) adv_enabled 0