Yeah, I believe I know what is happening. The database is being corrupted by the direct deletion of the spam posts. The indexing gets off. The index is NOT the database, it only holds pointers to locations where the data is stored. I believe this is what we are seeing.
Content is not lost within the database, and, the generation of a new index(often time consuming) will fix the problem. I am not sure who programmed the "Delete All Spammer Posts" button, but he should have forced a rebuild after it was used in the program after everything was deleted. I think that will fix the database/index mismatch. I might be incorrect, but I have done that myself with some data bases. DBIII, DBIV, and Access, and some others acted like that. Some are smart enough to know better and do it automagically with singular deletions and offer this after a multiple deletion, but as a seperate function. They offer low level deletions and rebuild funtions for these cases, too.