Partial remote control
Thanks for response David. No UAC prompt on remote PC and yes Quick support on remote. I can add that the freeze can be unlocked by getting remote user to close Ccleaner. Additionally the same freeze occurs when opening Task Manager on remote, same unlock method. ie Ccleaner and Task Manager cannot be controlled from master PC. Possibly other actions are similar, not yet discovered.
Having used Teamviewer for many years this is disappointing. I am trying to move from Teamviewer because they regularly block and a pain to get unblocked.