Hello @fred
are you using access control rules? If so, which conditions are enabled/used?
It's true that we have a fix in 4.1.5 which will prevent Veyon from using any groups at all for access control if the LDAP/AD group member attribute is not configured or the user object could not be queried from a user login name. So first of all please check your LDAP/AD settings and perform all integration tests.