zephyr: Bluetooth: Controller: Restarting BLE scanning not always working and sometimes crashes together with periodic. adv.

Describe the bug There are 3 sub issues, all related to the same scenario hence I made one ticket. Write if you want it split.

1. Restarting scanning with bt_le_scan_stop followed by bt_le_scan_start sometimes fails. bt_le_scan_start returns success, but scanning either not started or just a few events are received before it stops reporting anything from controller (maybe similar to https://github.com/zephyrproject-rtos/zephyr/issues/49915). Doing an additional disable/enable when this happens makes it working again.
2. There is a crash in Scan disable...ASSERTION FAIL [!aux->parent] @ WEST_TOPDIR/zephyr/subsys/bluetooth/controller/ll_sw/ull_scan.c:647 sometimes when calling bt_le_scan_stop
3. Sometimes bt_le_scan_stop returns -5 (I/O error) in the sample application, I don’t think it should.

• What target platform are you using? nRF52833, Zephyr
• Is this a regression? Not tested this scenario before.

To Reproduce Have 10+ tags sending per. adv. with 7.5ms interval and CTE enabled. Build and flash the application below. Then wait…

Application: aoa_receiver_multiple-gh-50432.zip

Relevant configs (see attached application for more info):

CONFIG_BT_CTLR_ADVANCED_FEATURES=y
CONFIG_BT_CTLR_SCAN_AUX_SET=2

CONFIG_BT_CTLR_SYNC_PERIODIC_SKIP_ON_SCAN_AUX=y

CONFIG_BT_CTLR_SCAN_AUX_SYNC_RESERVE_MIN=n

CONFIG_BT_TICKER_LOW_LAT=n
CONFIG_BT_TICKER_PRIORITY_SET=n
CONFIG_BT_CTLR_SCAN_UNRESERVED=n # Scan only when radio is free.

Expected behavior Scanning enable always works and no crash when scanning is turned off.

Impact An application cannot know if there are no devices in the area or if bt_le_scan_start did not work.

Logs and console output

1. Log for scan enable not working:

...
Queued: 7 Synced: 4 Num err: 0/62
[00:00:03.413,879] <wrn> main: RESTARTING SCAN AND SYNC...
Scan disable...Success.
Start scanning...success
[00:00:03.617,706] <wrn> main: RESTARTED!
Scan is running...
Running...
TAGS:sync...,26,sync...,sync...,sync...,sync...,sync...,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 7 Synced: 1 Num err: 0/26
[00:00:04.618,286] <wrn> main: RESTARTING SCAN AND SYNC...
Scan disable...Success.
Scan is running...
Start scanning...success
[00:00:04.821,289] <wrn> main: RESTARTED!
Running...
TAGS:sync...,sync...,sync...,sync...,sync...,sync...,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 7 Synced: 0 Num err: 0/0
Running...
TAGS:sync...,sync...,sync...,sync...,sync...,sync...,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 7 Synced: 0 Num err: 0/0
... Nothing happens

1. Log for the crash:

...
Queued: 11 Synced: 6 Num err: 0/79
Running...
TAGS:18,sync...,sync...,0,20,sync...,12,19,20,sync...,20,sync...,12,14,11,sync...,sync...,sync...,sync...,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 10 Synced: 10 Num err: 0/146
[00:01:33.819,915] <wrn> main: RESTARTING SCAN AND SYNC...
Scan disable...Success.
Start scanning...success
[00:01:34.024,810] <wrn> main: RESTARTED!
Scan is running...
Running...
TAGS:sync...,sync...,sync...,sync...,28,sync...,sync...,sync...,1,sync...,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 9 Synced: 2 Num err: 0/29
Scan is running...
Running...
TAGS:9,18,sync...,7,54,sync...,20,sync...,13,sync...,sync...,1,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 6 Synced: 7 Num err: 0/122
Running...
TAGS:16,16,14,10,17,sync...,15,10,8,sync...,1,16,2,sync...,sync...,4,sync...,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,-,
Queued: 5 Synced: 12 Num err: 0/131
[00:01:37.027,923] <wrn> main: RESTARTING SCAN AND SYNC...
Scan disable...ASSERTION FAIL [!aux->parent] @ WEST_TOPDIR/zephyr/subsys/bluetooth/controller/ll_sw/ull_scan.c:647
[00:01:37.028,411] <err> os: r0/a1:  0x00000003  r1/a2:  0x00000005  r2/a3:  0x00000004
[00:01:37.028,411] <err> os: r3/a4:  0x00000287 r12/ip:  0x200027ac r14/lr:  0x0000da55
[00:01:37.028,442] <err> os:  xpsr:  0x41000000
[00:01:37.028,442] <err> os: Faulting instruction address (r15/pc): 0x0000da60
[00:01:37.028,472] <err> os: >>> ZEPHYR FATAL ERROR 3: Kernel oops on CPU 0
[00:01:37.028,533] <err> os: Current thread: 0x20001c40 (BT TX)
[00:01:37.107,849] <err> os: Halting system

Environment (please complete the following information):

• OS: Windows
• Toolchain: Zephyr
• Commit SHA or Version used: (main as of now) e1cb0845b49b6a4100c9e5558d37667b92f0d000 with 894423e9aed34a394b97c995c33549513b0ac4a5