I am sorry to hear of your troubles etepbbb and others.
Definitely follow the advice already given by many other posters......as they will be much more helpful than mine (since I haven't experienced your problem).
I have owned my MkV combo for 2 years now with no problems whatsoever....manual or footswitching mode. 99% of the time it has been set to footswitch mode and has performed flawlessly. Maybe I am just lucky....dunno.
One thing I have noticed is most people that post a problem with the footswitch of the V are MkV Head owners. Clearly, this could be that more people opt for the head than the combo, but I still find it interesting?
Basically, the head and combo are identical with the exception of the combo including a cab and speaker. In fact, I would expect the combo to be less reliable regarding footswitch operation based on the additional vibrations that are inherent with a combo versus head?
Once again, the excellent footswitchable features offered with the V and the performance of my MkV combo, in general, have worked flawlessly for 2 years.
In fact, it is the excellent footswitchability of the V (along with great sounds in each channel) that make the V my preferred amplifier to play.
Best of luck in resolving the problem you are experiencing!