When a workflow stage reached its max number of concurrencies, and a build is aborted, this is not registered as finished builld/stage
Steps to reproduce:
1. Create a build with one stage and concurrency=1
2. STart the build
3. Abort build when stage started, but before stage is finished
4. Restart a build
The new build will tell you it is waiting for the build (that was just aborted) to finish. Wven deleting the build won't make any difference.
Workaround: increment the number of concurrent builds'
Maybe similar to: https://issues.jenkins-ci.org/browse/JENKINS-26709