Tried Safemode but it didnt help either

Hi Dober, sorry to hear about the crashes. I just don't see much explanation for it in that report:

MOZ_CRASH Reason (Sanitized) : MOZ_RELEASE_ASSERT(mWorkerThread == GetCurrentVirtualThread()) (not on worker thread!)

Hmm...

Safe Mode was a good test. Could you share that crash report ID as well to see whether it has more information?

Do you notice any pattern related to particular sites, types of content, length of browsing, or time of day?

You can create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile