Malformed crash reports generated by Unity Cloud Diagnostics

Starting today, all the crash reports are malformed and cannot be parsed on iOS/tvOS.
When the app crash and we're trying to recover, we can see this log in console.app:

CrashReporter: Could not parse crash report: An unknown error occured decoding the crash report

(that's the error thrown by plcrashreporter, at this line, https://github.com/microsoft/plcrashreporter/blob/master/Source/PLCrashReport.m#L295)

Anyone else faced the same issue?

 

https://forum.unity.com/threads/no-crashes-from-the-testflight-build-for-ios-13.962697/
I see log "CrashReporter: Could not parse crash report: An unknown error occured decoding the crash report" on this build now (after build on unity2020.3.14)

 

Also seeing this, I started exploring using unity cloud diagnostics crash reporting for our team due to an increase in the crash rates across our apps after the iOS 15 update. Testing on an iPhone 13, I am seeing exceptions only coming through to the dashboard. We are on Unity 2020.3.18f1

When I force the app the crash either with an unhandled exception or using UnityEngine.Diagnostics.Utils.ForceCrash with any of the types, I see no crash reports. I decided to use the CrashReport API to log the crash report as an exception, and I did see the exception, so the crash was reported, but it looks like it couldn't be parsed and so was empty. I saw this in Xcode:
CrashReporter: Could not parse crash report: An unknown error occured decoding the crash report
And the report that I printed out with Debug.LogException was empty. Here's what looks like the relevant log snippet.

Code (CSharp):

1. Stacktrace is not supported on this platform.
2.  
3. unsupported group tag at offset 65645
4. CrashReporter: Could not parse crash report: An unknown error occured decoding the crash report
5. UnloadTime: 0.466333 ms
6. unsupported group tag at offset 65645
7. CrashReporter: failed to init crash report
8. unsupported group tag at offset 65645
9. CrashReporter: failed to init crash report
10. Uploading Crash Report
11. Exception: Crash: 1/1/1970 12:00:00 AM:
12. UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
13. UnityEngine.DebugLogHandler:LogException(Exception, Object)
14. UnityEngine.Logger:LogException(Exception, Object)
15. UnityEngine.Debug:LogException(Exception)
16. CrashReporter:Awake()

I also see several posts from Unity folks on here recommending that people use Backtrace over this tool, is that still the recommendation for someone trying to evaluate what to use to track crashes and errors?