Baxi Combi Leaking?

hi All, i have a Baxi Combi boiler which had slight leak inside, a engineer came and drained the boiler and fitter new o rings. Sinc the fitting the joint is still moist ( not dripping as fast) and pressure is still dropping ( but very very little) BUT last night i checked the boiler and there was about 1 litre of water all over the floor and inside the pressuer gauge etc as if it had come out with force? but the pressure still looked ok on the gauge? i have checked the fill loop and this looks ok. Could it have been something the engineer has / or has not done when he fitted the o rings? Thanks