Can I reset POSIX ACLs for a folder?
Yes, you can.
Remove all ACLs.
tar from this article to remove all ACLs.
Transfer ACLs from a folder with correct ACLs.
First, configure the ACLs on a working folder as they should be. Afterwards, transfer ACLs from this folder to the target one:
getfacl folder_ok | setfacl --set-file=- /path/to/brokenfolder