Teamcity thinks agent is running a build, but it is not

Question

Using teamcity 5.1 (build 13360)

Usually everything works as expected

Occasionally it gets into a state where the server runs a build and it thinks the agent is running it, but the agent doesn't actually run the build

I see no sign of the build being run by the agent in its logs

So the build just runs forever on the server

I have restarted agents and the server

Answer 1

So it appears it recovers after a few hours

I just left a build running and it completed after a while

Don't know if restarting server / agents helped or not