The error on its own isn’t too concerning, but it is pretty odd, especially as it’s been there so long (13 years!) and I’ve never seen it triggered before.
Internally Matrix has a concept it calls “run levels” that it uses to determine if things like permissions checks, asset locking, triggers etc should be run. The error implies a web request downgraded one of those run level bits (e.g ran a block of code with triggers disabled) and failed to upgrade it at the end of the block.
If the error continues to come up, I think the best bet is to contact Squiz Support as we’ll probably have to modify some code to isolate what’s going wrong.