I have 3 nodes on the same server, and have seen this behavior before, and
it's happening now again.

My node 40821, 41618, 420 are linked and report as linked, but a user on one
doesn't bring the other up and vice versa.  A restart will clear it, but is
there any troubleshooting I can do to debug this problem?
"

Are the nodes on the same server or the same network?

David