Trauma with my Trumatic C3402

HI Ash

Like all possible causes,, it could be a number of issues,, sounds like over heating initially,

Temp sensing is taken from the wall switch, or if fitted, a room temp sensor,, check that these are clear from obstruction and away from another heat source.

Gas,, use red propane at this time of year, as the blue butane may not vapourise enough gas to keep supplying the boiler,,

I would imagine you have the heat set fairly high with low ambient temp,

check the four take of ducts on the underneath the boiler, as one or two of these may have become disconnected raising the temperature around the boiler..

Also if you have the temperature setting set to max, just bring it back a little and see if the unit will run for a longer duration..