Hi,
I have found that is necessary to provide permission to create SQL tables (in addition to SELECT, DELETE, INSERT, and UPDATE, which are already needed by WP). Things appear to work when either permanent (CREATE) or temporary (CREATE TEMPORARY TABLE), or both, creation is allowed. As I don't know all of the details of what is happening in the code, I have just allowed both, and things seem to be working fine. I'll let you know if any other issues arise.