They "undid 3 hours work on the climate display module" - what exactly did they do?? This lot sound like a classic bunch of "¤¤¤¤-in-your-cold-water-tank" plumber types ...
There is only one thing you can do on that module and it takes a blind 1 armed monkey 5 minutes.... that's what it took me anyway
(I haven't really only got 1 arm...)
Agree - check absolutely everything