Jenkins slave nodes hangs for up to 12+ minutes after build phase completes.

I have a master node and 7 nodes in the build pool. The master is configured to only run jobs labeled master. Builds are always only done from the build nodes.

There are no post-build steps configured.

Hang/delay is observed if the build step passes and/or fails.

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....
2019-09-16 16:51:45 ERROR: last command returned failure: 1
2019-09-16 16:51:45 
2019-09-16 16:51:45 build.bat failed with error code '1'
2019-09-16 16:51:45 
2019-09-16 16:51:45 Build step 'Execute Windows batch command' marked build as failure
2019-09-16 17:03:48 Finished: FAILURE
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Observe that at 16:51:45 the Build step for Execute Windows batch command finishes. However the build step continues for another 12 minutes before finally completed with the FAILURE notification.

There are 6 nodes in the build pool being triggered for the builds