wp_posts locks up when optimized – post_category and comment_count show “0”

When I repair or optimize my DB, the wp_posts table locks up, an error message appears of “Cannot create temporary table”, it shows as “Busy” in PHP MyAdmin and it and my entire DB becomes permanently inaccessible, locking up my site. All other tables are just fine and once I empty and restore the data in the wp_posts table, all works fine again.

In viewing my DB in PHP MyAdmin, I also find that in wp_posts, the columns of post_category and comment_count have values of “0” for every post despite each having assigned categories and comments. The database operates properly with my theme though, all posts appear under their correct categories at my site and display their comments correctly.

I wonder if whatever the issue is with wp_posts not being able to have a temp created when being repaired or optimized, is connected to this bug that prevents posts_category and comment_count from displaying values. Maybe they are unrelated but my priority is resolving the issue of wp_posts locking up every time the database is optimized or repaired. Appreciate any advice you can offer on this. Thanks!