In my case this seems to be caused by a bad batch of network cables(!). When swapping gear I also bought new cables, and one of the bags seems to contain some bad cables. First time for everything I guess, also teaches me a lesson for being cheap and buying "off brand" cables. When I removed the hot spare and set it up as a test network I also changed cable color to help with cable management, which is why it worked. I swapped out the original cables, and, for now at least, everything is quiet.
... View more
