a topology change?
ports going up / down - have you got "portfast" turned on for user ports - if not every PC reboot or move of a laptop will generate a topology change...
more serious issues would be about a flakey network - maybe a link in a loop that isnt working reliably.
it certainly doesnt help as they are unlikely to have statistics and logging to help you track down a problem.
find where they come from - start at the centre, note the stats and then clear them. trace outwards following the statistics. try to correlate changes with a device, habit of a user etc.
run some pings at 1 sec intervals thru the suspect bits of the network and see if you are losing packets or getting variable delays - if you have, then you have a problem to track down.
rince and repeat anywhere else with the issue.