Electric Shower: Triton Opal II

Soft water area. Stopcock fully open, water pressure is high. New hose and shower head, cleaned and checked for blockage.

My Triton Opal II has been progressively more intermittent in heating.
It always has been less effective in the winter, but now is barely heating.
When operated on the High II setting, low pressure light comes on and flickers.
If you're lucky, this dims a bit and the High setting slowly comes to life with some warm water.
Dial is normally at about the 1 o'clock position, but varying it has little effect except when turning it lower (anticlockwise) there is no heat at all.
TCO, Outlet, Tank, checked for continuity with multimeter OK, solenoid checked for resistance and at 3.7.
Tank elements (Red to Blue) show resistance of about 11.5.
No sign of any burning or damage.

Any suggestions please?

whats the pcb number ?

Number on PCB is

7073333

HK201435/E

although the last letter is a little smudged, but fairly sure it's an 'E'

Thanks for responding.

when the low pressure neon flickers check the pressure switch is making the bottom of the pcb micro switch.
if it isn't isolate the power and check the micro switch hasn't been pushed upwards and is loose.

these pcb's suffer with the m/switch being faulty and the m/switch coming loose and bending upwards and the pressure switch failing to contact fully.

Sorry seco services , been offline for a while.
Checked out the microswitch and seemed secure enough, but then noticed the no 1 relay had been arcing, and the no 2 wasn't operating at all. Rather than risk it, have indulged in a new shower in the sales.
Thanks for the advice anyway, much appreciated and I'll file it away for future use, no doubt.

if you do ever use it a pcb will sort the issue.