So far I’ve tried deactivating:
Autoptimize
Limit Login Attempts
Ninja Forms
Regenerate thumbnails
WooCommerce Menu Cart
WP Show Posts (deleted, wasnt required any longer)
I also just tried reinstalling Microsoft Edge, all had no effect on the flickering or lines issue.
I’m a bit weary about disabling Woocoomerce or GP Premium incase I lose anything after re-activating?