F1 setting on Protherm boiler?

I've got a Protherm boiler and on almost a daily basis it keeps "switching" to the F1 setting. I've checked the pressure and have ensured that this is set correctly, but it still keeps happening! Pressing the reset button does fire the boiler again so that I can get heating and hot water, but there's obviously something amiss and it's really inconvenient/annoying. When it goes to the F1 setting, I can't get hot water or heating.

Also, I've recently increased the water pressure in the house to try and get a better water flow in the shower. I can get hot water to all taps in the house (have checked the water temp on boiler and adjusted it accordingly), but can now only get tepid water from the shower. Does anyone know why this is and what I can do to get a hot shower please? Other than buy a new boiler?!!!!!