[david914]

The transformer buzzing is not uncommon, I wouldn't worry over it unless the noise is bothersome.

What you found is typical when you have large pins from a transformer, or another heat producing device, soldered to a circuit board. The heating and cooling causes the device and pins to expand and contract, eventually causing the cracked solder joints, particularly if the joint did not have enough solder, or wasn't cleaned well before applying solder.

I've found that if there isn't too much solder on the existing joint, just adding some while re-flowing the joint will take care of the problem. If the joint already has a good bit of solder on it, using a solder sucker and then re-soldering the joint is best.