I’ve moved it back over to support as you’ve managed to solve it yourself. 
Safe mode only disables certain elements of the plugins, though generally the pieces which are most likely to cause issues. In some cases they would need to be completely removed from your app.yml. It’s generally good practice to remove any unused plugins, especially third-party ones, if you’re not using them - and particularly if you’re experiencing difficulties that cannot be replicated here on Meta or on another test site.