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!)
They will just have to get better. These things never go away. Unfortunately, just like AFCI 1.0, 2.0 and 3.0, the customer is stuck with what they had to buy at the time, unless they want to buy new ones.
I have always been a big fan of electrical safety and the code has come a long way since it fit on one page but I think we are reaching the point of diminishing returns. We are coming up with expensive fixes to address a small fraction of a percentage of accidents. I suppose if NFPA can't write a new code every 3 years, they would be out of a job. I am starting to think it is more about jobs and selling books than safety.
The Cooper TR duplex receptacles that I used for one new house were pretty smooth operating, as well as the Leviton TR duplex, but the Leviton TR GFCI receptacles had that noticeable restriction the first time I used them. The P&S decorator TR receptacles I used for one kitchen remodel were also not so hot. They were made in China and had that same noticeable restriction when the plug-in tester was initially installed for the first time. After a good push and some wiggling, followed by a slight plastic pop or tick sound coming from within the receptacle, the tester could then be inserted and removed without any restriction. The other bad thing about these P&S receptacles was that the metal yokes were made very thin and would flex so much that even when properly installed, the thermoset wall plates could still sometimes crack when you did your initial plug-in testing at finish. I used to really like P&S, but won't be using those again.
I know it adds time to the trim but maybe you should do the initial "break" in with the receptacle on the floor before you install it. Then you can lean on it without stressing the yoke and if it is actually defective you are not wasting time putting it in and taking it out.
I recently renovated my sons bedroom and installed hubbell homeselect TR receptacles. There doesn't seem to be a break in period for these. It is extremely difficult to plug anything in. My 7yr old son got a shock trying to plug in a charger. He knows how to plug something in without getting a shock and I truely beleive that he only got shocked because these TR receptacles are so hard to use.
You know how I feel about those things. I don't believe the manufactures should be allowed to write the NEC, unless it is only about the parts of the NEC referring to construction of the equipment. Too many times a manufacture develops a new piece of equipment and then before you know it, it is the code as a requirement.