[c-nsp] 3750 taking errors on multiple ports

[Randy Bush]

some hours back, an antique Cisco WS-C3750G-POE-48 started taking output
errors on multiple ports.  they are generally vlan edge, a la

interface GigabitEthernet1/0/31
 description x.sea eth1
 switchport access vlan 10

shows output drops

antique.sea#show interfaces GigabitEthernet1/0/31
GigabitEthernet1/0/31 is up, line protocol is up (connected) 
  Hardware is Gigabit Ethernet, address is c40a.cb51.4d9f (bia c40a.cb51.4d9f)
  Description: x.sea eth1
  MTU 9000 bytes, BW 1000000 Kbit/sec, DLY 10 usec, 
     reliability 255/255, txload 5/255, rxload 2/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported 
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input never, output 00:00:01, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1532
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 11292000 bits/sec, 689 packets/sec
  5 minute output rate 22658000 bits/sec, 765 packets/sec
     2153269 packets input, 3859557279 bytes, 0 no buffer
     Received 68 broadcasts (4 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 4 multicast, 0 pause input
     0 input packets with dribble condition detected
     2416117 packets output, 9034236494 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

any clues on how to debug?  thanks.

randy