Auto Updates For Plugins Persist Even Though Disabled

I’m working on a site with plugins that I need to keep rolled back (nextgen gal), but for some reason the plugins auto update in the background. I know the auto updater in 3.7 has plugin updates disabled by default, so I don’t understand why this keeps happening.

I even manually disabled plugin updates with:

add_filter( 'auto_update_plugin', '__return_false' );

And I also used a plugin to manage this, but it still updates.

Is there any reason this would happen? I searched the theme and wp-config for signs up auto updates enabled, but found none.

Thanks!!