Problems with Baxi Boiler and interrupted Gas supply or flame fault?

You dont say what model your boiler is which may have helped as different models have slightly different operating systems but you do say its about 20 months old so has it been serviced in that time as if not it would support the idea of either a dirty electrode or possibly a dirty burner and the electrode is not in the flame properly so the boiler doesnt know its alight so it goes to lockout ie E133.