I just had the same Problem on 0.217.1, but I thought it was my fault (probably still was), as I completely filled up the disk on the VPS, so no data could be saved any more. (let’s not talk about that ) After that I got some rouge workflows which were in a running state but could not be found (same error message than you have).
For me, that just happened after changing the db to MySQL, so MySQL could not save anything and was in that state for about 2 hours.
I cleaned up the running workflows by changing the state of the workflows to “failed” in the database. (do not do that, at least until someone other says that is OK ^^)
Is there a better way of handling a case like this?
I’ve just checked, and I definitely could have done a better job on fixing them, I forgot to add a failed in time on some of them^^: