I had the same problem but found out that when I disabled and tried to re-enable my ProPhoto3 Theme Compatibility Patches plugin, it told me that I needed to actually delete this plugin and redo the process in order to update it. It’s the same plugin but for some reason I needed to go through this process in order to be the most up to date. It was odd because I didn’t get a message saying it needed to be updated, I only knew after I tried disabling all of my plugins to see where the problem was. Anyway, that fixed my picture upload problem! Hope that helps ; )
