Jobs do not resume after Jenkins restart

After Jenkins is restarted for any reason, ongoing jobs go into a stale state.

Job will try to resume, but get stuck displaying:

{{Resuming build at Mon Nov 27 17:25:51 IST 2017 after Jenkins restart }}
Ready to run at Mon Nov 27 17:26:00 IST 2017

Nothing further will happen.

The stage where this happens (python pytest) reads:

lock('server-gpu') {
bat '''
call activate py35
call conda env list
call python.exe -m pytest --junitxml=test_results_nightly.xml
'''
}

Not sure if this has to do with the lock. The job acquired the lock before the restart and after the restart, other jobs I start wait for the lock so it seems to have gotten it.

Any idea for a solution or workaround (which is not completely manual) would be appreciated.