What brand of incubator are you using?
If it's the standard foam type (Harris Farms Innovator, Hovabator, Little Giant, etc, with 2 small red vent plugs, I leave both of them off. I usually only have to add a tiny bit of water, once a day to keep the Rh up to where I want it. Mine are in a AC...
Just add enough water to bring the humidity up to 30 - 35%, it's really not that hard to control the humidity.
Is the incubator in an air conditioned room?...this will lower the ambient Rh in the room!
Tiny bubbles is an indication the egg has been 'scrambled', happens pretty often with shipped eggs. Also, do they float all around inside the egg when turning the egg while candling, that's a sign of a detached membrane.
I've had eggs not necessarily explode but open up because of the bacteria that got inside the egg, forced a fissure to open...a leaking, stinky mess. No cracks were noticed during candling. I candle all my eggs before I set them, checking for cracks, detached aircells, etc.
I've had them 'hold for pickup', and regular postal delivery.....for me, it didn't make much difference. The further they have to be ship does make a huge difference, also the packing material used and how they were packaged.
Although, I think 'hold for pickup' is better than having them...
Yeah, I've caught/scolded my post person, dropping my eggs over my front gate....5 ft. ...I don't get many to hatch when that happens...plus the rough treatment it has gone through to get here in the first place!