Dynamic braking should not be active if the drive is running. It should only limit high DC bus volts.
If there is a mechanical brake on the motor, definitely rule that out first. Those things are usually designed to get tighter and tighter as they wear...
What is the output current during this apparent stall condition? I would expect it to be too high.
Drive parameters don't go bad, but fat-fingers can be bad...perhaps something was changed inadvertently?
Motors can get weak over time, insulation can break down, mechanical systems can gradually degrade.
Is the drive running in sensorless vector mode?
I would record all the relevant parameters and try auto tuning it to see if it helps.
I recently had to troubleshoot a similar problem with a similar drive and nothing seemed to help.
Finally we found a pneumatic actuated bar that was causing interference that you could not see under normal conditions, and it was retracted during our first inspections. One of the guys manually operated the solenoid valve and found the bar installed backerdz...
But in your case, watch the motor current, investigate the control method (open loop vs. vector), and try autotuning if running in vector mode.
