Maven Process exited with code 137

When we run our maven tests either through the Maven Runner or through a Command Line Runner (using mvn clean test) it eventually fails with an exit code of 137, which appears to be an out of memory issue. The result of the build says Canceled with comment: unexpectedFinish

This build used to run fine and has only started failing recently with no updates to the code base. Same build agent. If I ssh into the build agent server, cd into the working directory, set up all the same env vars and run mvn clean test myself it runs fine, no memory problems.

Any idea why it is failing in TeamCity, but not when running it manually?