One thing I have been thinking the last few days is if there is some kind of funky bind in the binding table (more likely after a factory reset or after a different device gets removed from the network). This causes the switch to send out a lot of broadcast traffic to try to find the route for the device. Excessive traffic may fill up the memory on the switch. As annoying as it is, it might be worth it to factory reset some switches and recreate their binds to see if it makes a difference. Of course, doing a packet sniff would help see if this is happening and whether that would make a difference or not.