On a rare occasion of TeamCity server or agent process terminating unexpectedly with no reason, it can happen that this is caused by Java runtime crash.
If this happens, Oracle JVM creates a file named
hs_err_pid*.log in the working directory of the process. Working directory can be
<TeamCity server or agent home>/bin or other like
C:/\Windows/\SysWOW64. You can search the disk for the recent files with "hs_err_pid" in the name.
See also related description.