Right, let me re-use this thread – 18.09 is stuck because of the “hanging jobs” on packet-epyc-1. @grahamc: IIRC restarting that machine would solve this. (I’m fairly certain that I can’t help this situation through Hydra GUI.)
I’m not sure why. I suspect that system load shoots up sometimes; nixos tests are more sensitive to that due to various internal timeouts.
I just try to check channel status once or twice a week and “solve” such trivial issues (e.g. restarting jobs). 18.09 updated today, but unstable has at least one reproducibly failing test (even locally).