Halstead SBX 30 ?

One of our two SBX 30 boilers locks out due 'FLUE GAS TEMP EXCEEDS 95'C'. Condensate trap checked clear.
Lived with this for a week as second boiler copes OK.

Last night 2nd boiler locked out due 'LOCKED OUT FLAME SIGNAL'. Tries to ignite 5 times but stays locked out.

Apart from cold weather nothing else has changed. Are these faults related?