Update to 3.9.6.1 now that that's out to see if it helps.

Upgraded. Let’s see what happens.

Which firmware version did you use and did you use the .all file or the .rst file?

Did you use the recommended BT Version?

Used the .all file.

3.9.6.1 also just crashed. Firmware error.

2021/05/27 20:40:21 --

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firmware exception debug info

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EPC=806f951c, Cause=0080000c, Status=1100fc03, BadAddr=00000000, RetAddr=8069b480
exception id=3(TLB Store)
exception occured in IdleTask Timeout
task_id=112, SP=0x837a9ca8(3152 bytes free, 5808 used bytes)
system tick =168944821
CURRENT_VERSION : 3.9.6.1_R
get from address : 80004000

Dump CPU registers:

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$ 0: 00000000 fffffffe 00000000 00000006
$ 4: 00000000 00000000 837aa4a0 00000001
$ 8: 00000000 80c5c490 00000000 00000000
$12: 00000000 fffffffb 00000000 0000000f
$16: 00000000 00000000 00000000 00000000
$20: 00000000 00000000 00000000 00000000
$24: 00000003 819b0000 00000000 00000000
$28: 818a9e40 837a9ca8 00000002 8069b480

I think this is something you need to raise with Draytek Support.