Since upgrading from 1.35 to 1.37, environment variables at least in the Tag field of the "Execute Docker Command" -> "Push image" build step seem not to be resolved correctly anymore. It fails with the following error message.

23:04:27 Successfully built e10497dbbd44
23:04:27 [Docker] INFO: Pushing image ...kube-system/jenkins:${BUILD_TIMESTAMP}_${BUILD_NUMBER}
23:04:27 ERROR: Build step failed with exception
23:04:27 java.lang.IllegalStateException: The template variable 'BUILD_TIMESTAMP' has no value

Jenkins: 2.32.1
Plugin: 1.37
Docker: 1.11.2

Downgrade to 1.35 helps.