cannot resolve conflicts on changed files with removed files from master branch

when i try to merge the master branch into my branch, and i get a conflict of a file i changed and was deleted on the master branch, i cannot resolve the conflict.

when i want to launch the external diff command the external diff command does not come up and the waiting window stays open forever until i cancel it manually.

when i say resolve take theirs - it says the file is locked by the file system.

when i say resolve take mine - source tree crashes.

About says that i have version 3.4.3 not 3.4.3 beta, but could not select 3.4.3.

However the same behaviour was before i updated.