Products get removed from their categories when saved

[eckster]

Whenever I hit the save button in a product, it is removed from all categories that it is currently in. We migrated from Magento 1.9 to 2.1 recently, and this issue has been happening consistently on every product.

I checked and no errors are being logged to exception.log or system.log, the debug.log has several cache_invalidate messages, but I believe that shouldn't be related to the problem.

Even after saving a product once, if you save it again after re-adding it to the categories, it gets kicked out of them again.

Any ideas where to begin troubleshooting this?

[tkovacs]

Any answer to this? I'm having the same issue in 1.9.  We have a hidden category & every day the number of items in that category has decreased.  We need it to work desperately as we are managing our MAP items in this hidden category which restricts further discounting for these items.  If the products are not showing in there, then we can get in big trouble with our manufacturers!  Please help!