Append Query no longer an "operation supported for this type of object"

Question

My database has a load process that has been executing an append query daily without issue since October of 2020. Since a recent Windows and Office upgrade by the firm, we have started seeing intermittent errors that are causing load failure. Because I needed to make some updates to that process, I imported everything into a new Access database, decompiled and recompiled all code, and did a compact and repair to ensure no corruption was in the file. Now, one of my append queries to a table fails saying the "Operation is not supported for this type of object". I can run a select and make table query from the statement, so I tried to modify the statement to append from the table created in a make table query thinking the subtotals in the original query were causing the problem. That didn't solve the issue. Interestingly, the original query has been successfully running in the original database for the past several days. Other append queries that happen later in the load module also run without issue in both places...........in version everything is local and another I'm using a split database with the backend on a network server

I need to make some logic tweaks to the code, and I'm afraid to do them in the original if running a new compile will cause a failure. I'm at a loss. The query is long, but I would be happy to include it if it's needed. ANY help is much appreciated. The behavior is just so inconsistent I don't know where to begin.