Spanning Tree Issue - Maybe

Hi there,

Trying to figure out a really odd issue. This particular network has been running fine for ages with no issues at all. All the switches are N3024's either in single, double or triple stacks. I have one switch in the network that has suddenly starting dropping off the network.

There are three links into the switch, one fiber and two Microwave to ethernet and when the switch drops off I found that cycling the links at the other end would bring the switch back up. Further diagnostics show that if I leave one of the Microwave link ports disabled at the other end the switch stays perfectly stable. Enable that link and almost immediately the switch drops off the network.

Nothing has changed with regards firmware (although they do need updating) but I can't see why all of a sudden this one switch has started playing up. I also swapped the switch out for another one just in case it was a hardware fault but I'm seeing exactly the same behavior on the switch I've put in which makes me think it's some sort of config issue.

Any thoughts?