Your System Details shows;

Installed Plug-ins

20-20 3D Viewer for WEB - Mozilla Plug-In v5.0.94.0 2020 3D Viewer for IKEA - Mozilla Plug-In v7.1.0.15

If these are doing the same job, this could cause issues.

Product Firefox Release Channel release Version 50.0.2 Build ID 20161129173726

bp-5fa8a7ba-2e81-4915-910e-11b1b2161210 bp-b380a6de-dc86-48fc-80b6-d5c2f2161210

Signature: IsAboutToBeFinalizedInternal<T>

msmpeg2vdec.dll = Microsoft DTV-DVD Video Decoder

This is for Sumo's Related Bugs 1289075 NEW --- Crash in IsAboutToBeFinalizedInternal<T>

1186483 RESOLVED DUPLICATE crash in IsMarkedInternalCommon<T> or @ IsAboutToBeFinalizedInternal<T> +++++++++++++++++++++++++++++++++++++++++++++++++++++++ bp-a6d3cb95-a5dc-4449-ba99-dc4bd2161210

Signature: js::ConstraintTypeSet::sweep

This is for Sumo's Related Bugs 1287306 NEW --- SIGSEGV @ js::ConstraintTypeSet::sweep when archiving a message in Thunderbird

1220385 NEW --- crash in js::ConstraintTypeSet::sweep

1174997 NEW --- Crash in js::ConstraintTypeSet::sweep +++++++++++++++++++++++++++++++++++++++++++++++++++++ bp-968ecc4a-023f-458a-a6a6-b4cfa2161205

Signature: XPCJSRuntime::FinalizeCallback +++++++++++++++++++++++++++++++++++++++++++++++++++++ bp-0f295332-ebf3-49e4-9ac2-b7ef52161205

Signature: js::jit::IonScript::unlinkFromRuntime

This is for Sumo's Related Bugs 1054538 RESOLVED FIXED Crash [@ interpExitTrampoline] with js::jit::IonScript::unlinkFromRuntime and GC on the stack +++++++++++++++++++++++++++++++++++++++++++++++++++ bp-d23b4496-b345-423c-affa-b67b12161205

Signature: IsAboutToBeFinalizedInternal<T>

This is for Sumo's Related Bugs 1289075 NEW --- Crash in IsAboutToBeFinalizedInternal<T>

1186483 RESOLVED DUPLICATE crash in IsMarkedInternalCommon<T> or @ IsAboutToBeFinalizedInternal<T>

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac=Options) key, and then starting Firefox. A small dialog should appear. Click Start In Safe Mode (not Refresh).

Is the problem still there?

Many thanks for you response, FredMcD. I'm happy to remove both of these (kitchen planners) - but the problem predates the installation of those for a fair while, to be honest.

I'm not sure what the information below the line in your post refers to?

I've pasted details of some crashes which predate the plug-ins, if this is of any use.

bp-70b97e4d-f6ff-41ca-836a-9aca02161105 - 05/11/2016 21:41 bp-32d97ae8-723e-4f58-8d66-6930e2161105 - 05/11/2016 21:41 bp-0dfdf56e-5a13-4e72-adc8-7849c2161104 - 04/11/2016 16:26 bp-1e9a32bf-8d82-4a11-b8b1-47a102161104 - 04/11/2016 10:56 bp-5b5540b8-e9ce-458a-a1b1-33c6f2161030 - 30/10/2016 10:52 bp-5d32fe02-c4f0-4b91-b7df-c8f432161028 - 28/10/2016 21:39 bp-c2c07be8-5a4f-4e56-8a97-0f1912161028 - 28/10/2016 20:31 bp-42a97835-b566-49fc-a27c-9627d2161027 - 27/10/2016 22:12 bp-6baa6271-47ed-4f55-b906-b5e962161006 - 06/10/2016 20:33 bp-0ae269a9-c688-48db-9cf9-9bc702161004 - 04/10/2016 19:22 bp-6de53293-e454-4f1c-ab78-5b2f82161003 - 03/10/2016 21:54

Celaeno said

I'm not sure what the information below the line in your post refers to?

If you are talking about the bp-##################### and the Signature:----------------------------------------

that is the data from the crash reports. This information helps us to discover the problem.

The crash reports you just posted are for the prior version of Firefox.

Did you try Firefox in Safe Mode? Was there a problem?

BTW: https://support.mozilla.org/en-US/kb/update-firefox-latest-version 50.0.2

It would be difficult to assess whether starting Firefox in Safe Mode was actually addressing the problem. As you can see from the list of crashes, there are days where it might crash three or four times, and other days when it doesn't happen at all.