I've been having a problem in ArcGIS 10.4.1 when performing larger joins (either attribute joins or spatial joins)--that is, with around 2,000 to 6,000 points. The join seems to work fine, but then when I export the joined tables out to a new table (all this is in one geodatabase), some of the records are repeated. That is, I may start with 3400 points in one table, join another smaller table, and then export the result (also 3400 records), but end up with 3412 points in the new table (the 12 extra records seem to be duplicates).
Any idea why this is happening, and how to handle it? Is it some kind of internal memory issue?
So far the only "workaround" I've found is to select and then copy all the records in the joined attribute tables out to Excel, then import them back to ArcGIS and re-plot the points, which is fairly tedious. Splitting the datasets into 2 or 3 smaller sets also seems to resolve the issue, but again, is annoying. Any advice would be most welcome.