You may be affected by a Bitbucket Server bug that has just recently been resolved in release 4.11:
So if your configuration matches the issue description, an upgrade to Bitbucket Server >= 4.11 might/should solve the problem accordingly - that being said, the ongoing discussion on the related and still unresolved Bamboo issue has not yet confirmed whether that is always the case, insofar one communicated workaround for Bitbucket Server < 4.11 does not seem to work:
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