mixpanel-swift: Potential iOS 15 crash related to Mixpanel

Hi,

We started to see a high number of crashes yesterday (13 Jan). They come from different app versions, and we never had that crash before.

This is a fragment of the stack trace of the thread were the app is crashing:

Crashed: com.apple.network.connections
0  libquic.dylib                  0x69938 qlog_abort_internal
1  libquic.dylib                  0x69924 qlog_abort_internal
2  libquic.dylib                  0x639e4 quic_frame_write_PADDING
3  libquic.dylib                  0x9c6dc _quic_packet_builder_assemble
4  libquic.dylib                  0x2490 quic_packet_builder_assemble
5  libquic.dylib                  0x366bc qui_assemble_and_encrypt

It seems that when this crash happens, Mixpanel SDK (v2.8.3) is performing some work on its network thread. We noticed that all the crash stack traces follow the same pattern.

com.mixpanel.74dc35f5daf1026de3ef7dff4d7ea18e.network)
0  libsystem_kernel.dylib         0x1540 semaphore_wait_trap + 8
1  libdispatch.dylib              0x4bf0 _dispatch_sema4_wait + 28
2  libdispatch.dylib              0x52a8 _dispatch_semaphore_wait_slow + 132
3  libswiftDispatch.dylib         0x1994 OS_dispatch_semaphore.wait(wallTimeout:) + 24
4  Mixpanel                       0x4d294 Flush.flushQueueInBatches(_:type:) + 156 (Flush.swift:156)
5  Mixpanel                       0x4c38c Flush.flushEventsQueue(_:automaticEventsEnabled:) + 89 (Flush.swift:89)
6  Mixpanel                       0x23038 closure #1 in closure #1 in MixpanelInstance.flush(completion:) + 1144 (MixpanelInstance.swift:1144)

Have you made any BE changes recently that could have caused this?