Just a quick Observation: I have run into the same error, both with PaleMoon and the Citrix ICA client. (on ArchLinux)
I had maybe a crash every 1-2 weeks, after setting MOZ_OMTC_ENABLED=1 a month went by without a crash.
Next I will try taking that out, and running both PaleMoon and the Citrix Client with LIBGL_DRI3_DISABLE=true for the next month, and see what happens there...
Support and discussions for the x86/x64 Linux version of Pale Moon.