Sometimes join records that were deleted from a system still show up in join data, so when the join data is mapped in to merge on idno, it should not create a new record (like defunct administrative data for example should not create new object records).
By join data, do you mean in the AMNH data? Or are you referring to a bug in CA?
Yes, amnh data, not a bug. But also other systems have the same issue. Like for Kress, they have a data set that is joins of objects to acquisitions but they also have a main acquisitions data set and a main objects data set. They may not want new object records or new acquisition records created when the join data imports.
Added new "mergeOnly" mapping level setting that will prevent creation of new records when existing record policy fails to match an existing record.
This is in develop and dev/representationBundle branches