old terms i know, but is the master also the VMD? They call it something else, but it is possible to have your media managers and volume managers be on a different server. You can find this sometimes in very large environments with multiple masters.
If not, can you do an output of bpps -a on your master server? I am curious if its not showing the processes running on its end.
I hate this error, its just looks messy. It really should be more tolerant of network latency. I would guess thats the issue. I mean how many times is it really a problem when they are partially online. That situation never is helpful to me. If they are off line, then yeah. I can go restart NBU on that server, and i will be back up. But partially online can be ignored. Which is why it should not happen. If I can ignore it why have it.
I was told that just wait for 6.5.3 it will be fixed, then 6.5.4, and i am there and its less, but i still get every one of my servers to show partially available from time to time. You can toy around by disable data collection, then enable it, and that will bring one back fully online, but i nolonger bother.