Worcester Junior 28i?

I have had Junior 28i boiler for just over two years (so it is out of warranty) and have recently started to experience problems. The boiler will cut-out whilst using the hot water (shower) and shortly after the heating comes on. When it "cuts-out" the reset button is flashing once/second which led me (and an engineer) to a list of potential problems on the diagnostics - none of which were easy to spot.

Are there any known issues with this boiler?

It didn't help that after the engineer had inspected/hoovered the boiler it worked flawlessly!

I do not believe it is the water pressure as current pressure is above 1 bar and does not change when not in use. Engineer checked for gas pressure and this is also OK.