OK, found a post from April 2018, where you briefly mentioned a memory leak:
It’s a VERY efficient action/condition. I would call it magical. I love it. I use it so much it could be the reason I am experiencing memory leaks with the KM engine.
This was clearly before Mojave (10.14). So, if it was the same problem, then it would have persisted through the Mojave update.
So, my guess would be that it is related to some older macro(s) from 2018, maybe in interference with another application that you are using frequently for the last year.
Your mention from 2018 was in the context of the Find Image action, which is one of the more “heavy-weight” KM actions.