Can anyone help identify the Add-On [or recognise the library etc] that is causing the pile up?

Neonisys

Any help would be most appreciated.

perfiction

If you ask about the victim then it's AwesomeGuildStore. If you ask about the offender then other addon/lib (most likely very old addon with embedded LibStub trying to load older version of LibAddonMenu-2.0) causes it to crash.

Baertram

I think this happens if you got PerfectPixel enabled (as I can see by your background: You do have this enable)
together with other addons like AwesomeGuildStore and other addons.

Addons with a total UI change like AUI also could cause this so try to disable all addons and only enable
PP + AGS and try if you can reproduce this error.
If yes: Write to the addon comments of PerfectPixel how to rebuild that bug.

If no: Enable other addons one after another, start with the ones that change the UI in total, like AUI.
See if this makes the bug reproducable.

If yes: That other addon (e.g. AUI) causes it and you need to write to the addon comments of that addon at www.esoui.com how to rebuild the bug and ask for a fix.

It's time consuing I know, but the only way to find out what causes it in combination.

e.g. I'm using 120+ addons (not AUI though) and it works fine for me. Never had any issue like that with PP and AGS.
But this also could not only be dependent on the used addons but their settings too. e.g. enabling setting1 at addon 2 could cause this to happen. I maybe not using setting1 but addon 2 is enabled too....

Hard to find out without testing this at the local computer where the problem happens...
Good luck!