I recently rewired a small house, and installed 46 of Leviton's tamper-resistant receptacles. This was my first major experience with them, and this is my report.
Devices were both Ivory and White, so we know there was at least two production runs involved.
My experience has been: insertion of 2-prong plugs can be problematic, especially if this is the first time the receptacle has been used. Even three-prong plugs seem to 'pause' the first time the receptacle is used.
Mind you, I AM talking about new appliances with UL listings. We're not talking about damaged / worn plugs or ancient stuff made before the TR standard existed.
I suspect that there's a wee bit of plastic flash within, that needs to be torn free for the shutters to open the first time.
I also suspect that the larger neutral blade on the 2-prong plugs is the cause of the insertion difficulties. The larger prong wants to enter first - as designed - and that can be just enough to lock up the shutters. Again, this varies by appliance, and seems to lessen after the receptacle is used a few times.
I'm not surprised; the neutral blades have been deliberately engineered to be larger and to make contact first. The receptacles are designed to require the prongs to enter at the same time.
We have two "in the name of safety" doctrines in conflict.
All I can suggest is that you use your plug-in tester to check EVERY receptacle for function, and explain this to the customer.
Opinion: TR needs to fade away. (OK, it wasn't very hard to persuade me!)
