Interactively rebase always aborting when a merge is necessary

When I try to perform an interactive rebase on a series of commits, if I squash together commits and check amend comit (or don't) that require a merge to fix conflicts, then it fails every time (which it should), but when I hit close the whole thing aborts and cancels the rebase, instead of letting me perform the needed changes

I can manually perform the rebase if I start it from sorucetree but don't hit close after it first fails. However, that's through the terminal, and just a workaround, and will not be accepted by the rest of my team.

We are planning to use this for a workflow with pullrequests and merging the code review changes together with a squash/fixup, without this we can't do use the GUI for everything.

I can reproduce this locally with a virtually trivial merge... take a code file, add 3-4 commits in a row to a branch each only adding an additional adjacent linefeed. This forces a merge and the above described problem.

I was told this was fixed for 1.6:
https://jira.atlassian.com/browse/SRCTREEWIN-1880

However that does not appear to be the case.

I have a question on answers as well:
https://answers.atlassian.com/questions/10392524/comments/10392756