I can no longer find the contractor who installed this in our bathroom and the whole handle seems like it's loose (there is a lot of room between the temperature cover and the main handle that turns the water on and off. How do i tighten this? every time i push it just moves with the internal parts.
also - how do i take the temperatur control cover off? commonly it needs an allen-wrench to remove these things but i don't see this item as having one.

It is either too hot or too cold.

I have this in my master bath for a few years now and love it, but starting a few months ago, the water pressure seemed to be slowly diminishing. Thinking I might have developed some sort of sediment in the valve, I removed the valve and flushed the lines. When I replaced the valve, the water pressure was even worse than before. Pressure is not issue with the valve out.
So, thinking that the valve was damaged/worn, I ordered a new cartridge and installed. Now, the water will either not run, or just trickle. Again, with the valve out, the water pressure if fine. It almost seems like the pressure equalizer is stopping the water flow for some reason. When you first turn it on, you can hear the water pressure kind of thump, then nothing. Turn off, wait a few seconds, and do it again and the same thing.

Did I receive a bad replacement??