sourcetree.log is attached (it's the last error, you may find some other issues to fix in the previous logs so I kept them)

The repro steps are easy in our case :
1. Have some local uncommitted changes
2. Try to pull from server (there has to be some changes to pull)
3. Click on Close button when the error message is displayed (failed to pull because of uncommitted changes)

The rebase after pull option may have been selected here.

Our repo makes use of subrepositories.

The issue appeared with 1.6.9 and is still occurring with 1.6.11.