To reproduce:

Unzip the attached archive and open in SourceTree
Right-click on first commit and select "Rebase children of 076e6f7 interactively"
In resulting dialog, drag 2nd-last commit onto last. Repeat two more times.
Click OK.

Expected result: squashes the four commits into one.

Actual result: Dialog with text below; closing it says "aborting rebase"

git -c diff.mnemonicprefix=false -c core.quotepath=false -c "sequence.editor='C:\Program Files (x86)\Atlassian\SourceTree\stree_gri'" -c "core.editor='C:\Program Files (x86)\Atlassian\SourceTree\stree_gri'" rebase -i --autosquash 076e6f7dbcce1c62ad63b13b23c0edae8bb447b5
Rebasing (1/5)

error: could not apply cabeaac... Bullet for ‘push -f’

When you have resolved this problem, run "git rebase --continue".
If you prefer to skip this patch, run "git rebase --skip" instead.
To check out the original branch and stop rebasing, run "git rebase --abort".

Could not apply cabeaac66a412d0bd06ac3e0bd04c93b4aa3a13e... Bullet for ‘push -f’

Completed with errors, see above.

Note: squash can be done successfully if the commit labeled "Bullet for ‘push -f’" is first renamed removing quotes and hyphen