Cham, it sounds like it may be a switch/power problem. For example, my Star Choice dual satellite quad output LNBs work fine with a 4x1 DiSEqC switch, but they don't get enough power through the EMP Centauri 8x1 DiSEqC switch. It does the same as you get, no signal and no quality. It has done this when the 8x1 was on the Pansat or the AZBox. The LNBs are on a 4x1 to the Pansat and on the 8x1 to the AZBox. Just have to tune in one of the satellites on the Pansat, and then I get signal on the AZBox for both satellites. Only rarely can I tune to one of those satellites without the Pansat also being tuned on that LNB.
So, try and figure out whether it is a switch problem, whether it only does it on certain satellites, etc. As well, I see you have a MicroHD which is connected to one LNB that is also connected to the AZBox. If it does it on that LNB, check if it does it when the MicroHD is also turned on and tuned to that satellite.
Since you do get the signal back after changing transponders/satellites, it may just be that the DiSEqC commands aren't kicking in for some reason.