Bamboo auto merge no report to Bitbucket

[Craig Tyler]

Bamboo 7.0.4, Bitbucket Server 6.9

We have Bamboo plan branches setup with Branch merging enabled and push on success. Everything is working as expected except warnings generated by merge builds are not being reported in Bitbucket pull requests.

1. Pull request A opened that is already up-to-date with master
2. Bamboo creates plan branch for A and builds without auto merge
3. Build warnings are displayed in the pull request A overview and inline on diffs
4. Different pull request is merged to master
5. Update pushed to pull request A, but does not address existing warnings
6. Bamboo performs a new build on plan branch A with a merge from master
7. Bamboo pushes merge update to Bitbucket but does not seem to also send build warnings to Bitbucket for the merge build
8. Build warnings are no longer displayed in pull request A

This issue prevents us from properly addressing warnings prior to merge if the last update was an auto merge.

I used the Bitbucket API Browser to check for a report at the merge commit id and it looks empty.

{
  "size": 0,
  "limit": 25,
  "isLastPage": true,
  "values": [],
  "start": 0
}