As noted below we have been in endless battle with the Filemaker Script Engine on the server. Windows and Mac with FMS16 - though we have seen it in FMS 14 and 15 as well, and have read about it in FMS 17.
There has been speculation that the FMSE doesn't handle script errors very well.
101 - record missing - can suppress by Get(FoundCount) = Get(RecordNumber) in lieu of GoToNextRecord exit after last
401 - no records match the request - kind of stumped here - a found count of 0 seems natural if it is true but FMP seems to disagree.
We are struck that we can defeat the 401 (would be funnier if it were a 404) by doing this. So we make sure every table we search has a "Please Find Me" record and write some findable text into a systems field - "Please Find Me". (ignore here the sequential# type of things - more complex but can be handled). Then we construct our find and just before the Perform Find we add a new request for the "Please Find Me" field.
A FoundCount of 1 now means 0 of what we wanted so 1 actually = 0. And we code accordingly. Is there a better way?
This is in relation to all this FMSE stuff. Maybe the FMSE can't deal with "soft" errors?