I have been using one of these consistently for indoor lead climbing for 3 months now. Probably about 4-6hrs per week. Love it in use but I have one issue with it.
When a climber who is light takes a fall and activates the locking mechanism there are instances where the locking mechanism activates but the shoulder does not release/pop up. Device catches the fall no problem but you can’t release the locking mechanism without 1st loosening the grip on rope to pop shoulder up to then take in the rope to release lock. At all times the lock is in place but it is rather disconcerting.
I thought I was going mad but a guy came over whilst this had happened and asked to see. After we let my daughter down we replicated a gentle fall which could activate the lock but not the shoulder.