workflow-api plugin version 2.6.
For the given pipeline script, secondLevelNestedBranch1 and secondLevelNestedBranch2 parallel branches are nested inside nestedBranch.
There are missing StandardChunkVisitor.parallelEnd() and StandardChunkVisitor.parallelBranchEnd() events for nestedBranch. This causes computing incorrect DAG and status of individual branches. Blueocean extends StandardChunkVisitor to process events and create it's DAG.
If there are only one parallel branches in nested parallel then no parallelEnd or parallelBranchEnd event is fired. See the script below: