Rust in thermostatic shower filter

[Tomat35]

Hi
I’m having problems with a luke warm thermostatic mixer shower.
Here’s what I know-
It can be hot for 20 seconds then goes to luke warm and won’t heat again.
The taps work fine however take a moment to get hot again after the shower has been used.
I have had a pressure valve fitted but not made a difference.
I’ve even fitted a new shower but not solved it, however on removal of the old one (still only a few months use) the cold water inlet filter was rusty.
Is that a clue to the problem or is it ‘simply’ the boiler is struggling?

 

[Tomat35]

No answers for this one then.
The rust can’t be a good sign though.
Turns out the cool shower was because the water temperature was turned down to 30 on the remote thermostat, simple really!