[Mists Classic]BugGrabber error (couldn't find an issue tracker for it)

[Road-block]

Describe the problem

What specific version of classic WoW did this happen on?

Mists Classic 5.5.3

What steps will reproduce the problem?

No clear reproduction case, at a guess when execution time exceeds the client limits?
The errors only show in the default chatframe, not captured in BugSack.

Attach a screenshot below to help describe your issue (Attach directly, do not link to other websites)

What version of the addon are you using? (Stating 'latest' is not useful)

BugGrabber 11.2.5 / BugSack 11.2.8

Do you have an error log of what happened?

See image above

Any additional information? (example: WoW language if not English)

This started happening sometime in the last few updates (at a guess around midnight compat)

[funkydude]

Was this during a raid/dungeon?

[Road-block]

I've seen it both in instances and outside world, in conjuction with weakauras or reforgelite for sure but occasionally unrelated to the operation of those two addons. Can't give a clear reproduction case.