Glowworm Compact 80e pressure rising?

Hi,

Ive recently had low pressure on the central heating system, so bled radiators and used filling loop to top up. (made sure that this was fully turned off.

Anyway, filled to 1.2bar but recently the pressure has been rising to over 2.5, and not showing much sign of stopping. (takes overnight to raise pressure)

I've bled the pressure out of a radiator back down to around the 1.5 mark, but it keeps going back up.

I can't find any info on what the max pressure is, dial goes from 0-4 bar, could i test it to 3 without worrying about anything bursting?

Any advice greatfully received.

Ta
don