Update: This is resolved as of version 6.5.5.2 of the client.
We have identified that recent Windows Updates have introduced a bug which affects the Bria Windows Softphone and can cause the application to crash.
This crash is related to components used in the Call History section of the application, and several users have reported that keeping this section of the phone closed/hidden has helped to mitigate the crashes.
We have also narrowed down the following specific Windows updates as the cause of the crashes:
Windows 10: KB5018410
Windows 11: KB5017271
When uninstalling those updates, the crash is no longer reproducible. This is another possible workaround, although uninstalling an operating system update is something users may do at their own risk.
Our engineers are still working towards a permanent resolution in the meantime.