I was looking round to select my next indoor route and observed a belayer pulling an armful of slack through his belay device. He was looking up at the lead climber while doing this. After pulling rope through he took his hand completely off the dead end of the rope. Without looking down, he fished around in the air with his hand to re-find the rope and took hold of it again closer to his belay device. He had no hands on the device for approximately 2 seconds. He repeated this a few times before I went to the reception desk to suggest the staff take a look.

He had a plain tubular belay device with no assisted braking.

From the desk, there is no view of the climbing area. After a couple of minutes, the staff member from the desk came to look, but by this time the "belayer" was now climbing.

The staff member went back to the desk and the "belaying" started again with the same error. If the climber got dropped without me saying anything, I knew I'd feel really bad, so, not wanting to distract him even more, I waiting nervously for the climber to get back to the ground I went over to politely point out the problem.

The belayer argued there was absolutely no possibility he could ever have taken his hand off the rope.