Since November 29 I keep finding a few of my WordPress sites with all of their plugins disabled (except for one called "Manage WP - Worker"). Each time this happens, it seems that there's an error at the top of the plugins page in WordPress that says:
The plugin 1 has been deactivated due to an error: Plugin file does not exist.
I've done some searches in Google to see if anyone else has experienced this, but so far I've only seen that people are showing a different error; one that actually contains a plugin name/php file instead of the number 1, like in my error.
When I find all plugins deactivated I can simply activate them again, and then it seems that the sites will be running fine for several days. Then the problem reoccurs.
What could cause this? Could it be orphaned tables in the WordPress database? I can, by the way, with nearly 100% certainty say that my site hasn't been hacked; I've got an awesome security plugin called BulletProof Security Pro and also checked out my site with Sucuri's free security/malware checker and no malware was found.
I've contacted my hosting provider, the company that makes the "Manage WP - Worker" since theirs is the only one that ever stays activated, and also BulletProof Security Pro, but the responses I've gotten from each is that: 1) I or another webmaster is manually deactivating plugins 2) I or another webmaster are deactivating the plugins via the database somehow 3) There's a hack
I can rule out each one of these three. So, I'm reaching out here to see if anyone has any ideas about what's happening.