Try another battery to start with. From what your saying, it sounds like the battery is low power(or **** brand) and is struggling to power the marker.
Try a duracell. Is there no way of turning off the beep?
nope, the solenoid it's self is quite odd and pretty noiseless, due to the way it works, I know how, just a bit of an arse to explain, and I suck at explaining in words
I dont know much about vibes but from what iv seen it the first post that it stops working after a few shots, and i know this has already been mentioned but i think its the Co2 freezing up the internals.
1 More time, try a battery(sorry, cannot stress this enough, I teched markers for years, and was quite often the 'fault')
2, Take out the battery, press and hold the power button, attached battery while 'on' if it blinks twice, do it again until it blinks once. The dwell will then be set up for co2.