In rare circumstances, incrementing output drops result from a problem with the transmit queue for a VC. During this condition, the VC appears "stuck".
Use these tips to determine whether you are experiencing a stuck VC condition:
Execute several instances of the show interface atm command and look for a rapidly increasing value for output drops.
If your image supports per-VC queueing, execute several instances of the show queueing interface atm command and look for a consistent value of "Output queue 40/40" if your VC uses Layer-3 FIFO queueing.
Execute shutdown and then no shutdown on the interface or subinterface. These commands reset the transmit ring queues.
Execute show atm vc and show atm pvc and analyze both the input and output packet counters. Are the input packet counters incrementing? Is the problem on the transmit side only?