The crashdump points to the encoder:
(can't post all)
Incident Identifier: 3A089DC7-D703-49B8-A82C-1CA5D4D495F1
CrashReporter Key: 4e9fa228fb3a1aacd70bccacf77cda7a60302e68
Hardware Model: iPad11,6
Process: com.apple.WebKit.WebContent [372]
Path: /System/Library/Frameworks/WebKit.framework/XPCServices/com.apple.WebKit.WebContent.xpc/com.apple.WebKit.WebContent
Identifier: com.apple.WebKit.WebContent
Version: 8612 (8612.2.9.0.20)
Code Type: ARM-64 (Native)
Role: Foreground
Parent Process: launchd [1]
Coalition: com.apple.mobilesafari [499]
Date/Time: 2021-11-13 23:51:03.9349 +0100
Launch Time: 2021-11-13 23:49:02.7432 +0100
OS Version: iPhone OS 15.1 (19B74)
Release Type: User
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000000
Exception Codes: 0x0000000000000001, 0x0000000000000000
VM Region Info: 0 is not in any region. Bytes before following region: 4366024704
REGION TYPE START - END [ VSIZE] PRT/MAX SHRMOD REGION DETAIL
UNUSED SPACE AT START
--->
__TEXT 1043c4000-1043c8000 [ 16K] r-x/r-x SM=COW ...it.WebContent
Exception Note: EXC_CORPSE_NOTIFY
Termination Reason: SIGNAL 11 Segmentation fault: 11
Terminating Process: exc handler [372]
Triggered by Thread: 16
Thread 16 name: EncoderQueue
Thread 16 Crashed:
0 WebKit 0x18f708f18 void WebCore::RemoteVideoSample::encode<IPC::Encoder>(IPC::Encoder&) const + 36
1 WebKit 0x18fcf8a04 WebKit::encodeVideoFrame(void*, webrtc::VideoFrame const&, bool) + 708
2 WebKit 0x18fcf8a04 WebKit::encodeVideoFrame(void*, webrtc::VideoFrame const&, bool) + 708
3 libwebrtc.dylib 0x1e9eace44 webrtc::VideoStreamEncoder::EncodeVideoFrame(webrtc::VideoFrame const&, long long) + 3336
4 libwebrtc.dylib 0x1e9eb19f4 webrtc::webrtc_new_closure_impl::ClosureTask<webrtc::VideoStreamEncoder::OnFrame(webrtc::VideoFrame const&)::$_13>::Run() + 5376
5 libwebrtc.dylib 0x1e9e47e94 std::__1::__function::__func<webrtc::(anonymous namespace)::TaskQueueStdlib::TaskQueueStdlib(std::__1::basic_string_view<char, std::__1::char_traits<char> >, rtc::ThreadPriority)::$_1, std::__1::allocator<webrtc::(anonymous namespace)::TaskQueueStdlib::TaskQueueStdlib(std::__1::basic_string_view<char, std::__1::char_traits<char> >, rtc::ThreadPriority)::$_1>, void ()>::operator()() + 920
6 libwebrtc.dylib 0x1e9ce6b38 std::__1::__function::__func<rtc::PlatformThread::SpawnThread(std::__1::function<void ()>, std::__1::basic_string_view<char, std::__1::char_traits<char> >, rtc::ThreadAttributes, bool)::$_1, std::__1::allocator<rtc::PlatformThread::SpawnThread(std::__1::function<void ()>, std::__1::basic_string_view<char, std::__1::char_traits<char> >, rtc::ThreadAttributes, bool)::$_1>, void ()>::operator()() + 260
7 libwebrtc.dylib 0x1e9ce6504 rtc::(anonymous namespace)::RunPlatformThread(void*) + 64
8 libsystem_pthread.dylib 0x1f01469a4 _pthread_start + 148
9 libsystem_pthread.dylib 0x1f0145ea0 thread_start + 8
...
