"Unable to merge" error when trying to merge a pull request

Received the following error message when trying to merge a pull request (see attached screenshot):

#!
Unable to merge
An error occurred saving this pull request

story:

• two repositories exist: Parent and Child (cloned from Parent)
• pull request created by Child repository
• go to Parent repository
• attempt to merge pull request
• RESULT: process for about 5 minutes then receive error message stated above
• EXPECTED: merge completes and no errors

notes:

• pull request contains two commits that were stripped from the child repository
• may be related to BCLOUD-8283