In my experience, the bearings of the motor are adversely affected when improper lubrication occurs (this covers many things: lube frequency, amount, mixing incompatible greases, etc). Rolling element bearings sometimes will exhibit bearing fault frequencies under some circumstances that "go away" or are reduced after lubrication. The key is to recheck vibes after some run time to see if the faults return or trend up into alert or warning ranges.
Some of the symptons/conditions you mention are independent of bearing lubrication, unless the bearings are damaged to the point that extreme looseness occurs that changes the mechanical alignment or tolerances of the machine. I would suspect that you would see major bearing faults and thermal problems manifest themselves before some of the other symptons you mentioned occcur.
We have found that many of the mechanical problems noted were due to "soft-foot" or alignment of the machines that can be aleviated by proper alignment and installation procedures.
If the some other symptons continue after proper alignment/setup, and assuming lubrication requirements are correct, then you are looking at the rotor or stator problems.
I would be extremely cautious accepting the answer to simply grease a motor based on "any problem" detected. There is a possiblity of masking a bearing problem until the next monitoring frequency or overlooking mis-alignment or foot related problems that might exist. It is necessary to reduce the variables by verifying/refuting/correcting the causes in a deliberate troubleshooting process.
Unfortunately, I do not have any good articles to refer to you and offer my sugesstions based on experience. A good place to start is with some of the vendors that offer your vibration analyzers and groups like the Vibration Institute or Technical Associates of Charlotte that provide machine vibration training.
Hope this helps and good luck.
