after deleting the vendor directory you need to relaunh composer update. it should force all sources to be installed clean.
But that error looks like something else. Maybe an error from the refractoring. I wil lool first thing tomorrow. If you wish touse eXp acan just switch to stable and composer update.
Edit : I confirm bug from code cleanup. I need my other computer to fix it so it will need to wait tomorrow morning; I don't have anything to test it on this one. sorry
Edit : Reaby is looking into it should be fixed soon.