Crashlytics empty stacktrace in android - crashlytics

Question

I faced with problem in crashlytics ndk stacktrace parcing. All or particular lines in stacktrace is "missing".
I simulated crash on device ( nullptr SIGSEGV ) and got human frienly stacktrace in logcat with correct functions names.
At next session crashlytics properly sent the report, but in Fabric's dashboard I see that this crash has "missing" lines, despite the fact that it's correct in logcat.
The chance of the properly crash parsing increases when I upload the symbols. But only for the last build and not for all crashes.
It means that crashlytics stores only single symbols copy for all application versions so old version will send stacktrace with "missing" lines.
After all of that, I try to investigate mechanic of catching and parsing crashes in Android and create my sigaction catcher with libunwind.
It's give me the correct stacktrace which I put to crashlytics payload ( context->log() ).
Next, I return signal to crashlytics sigaction handler.
Finally, I have "missing" lines stacktrace in Fabric's report and valid stacktrace in my payload.
Sometimes this approach causes crashes in OS below android 8.0, I think its because I use non-safe-signals functions, but it still works on android 8+.
Also I created linker map file (-Xlinker -Map=output.map), but I can't link it with fabric report istead of my self-made stacktrace.
So, the question is: why the lines in crashlytics stacktrace is "missing" in this situation while logcat and simple sigaction catcher provides correct stacktraces?
Versions:
crashlytics 2.9.3
crashlytics-ndk 2.0.4
Code:
Fabric.with(context, new Crashlytics(), new CrashlyticsNdk());