External Diff/Merge tool bug

[R_ K_]

While evaluating different external Diff/Merge tools in sourcetree, independently of what I adjust in the options, the application permanently selects Beyond Compare 5 as a merge tool.
Even after deinstalling Beyond Compare and sourcetree (together with the Atlassian folder) this issue remains.

Interestingly this issue just applies to merge not to diff. In addition, I have to state that the adjustment of different merge tools worked until some more testing with different

arguments with Beyound Compare 5. Used Sourcetree version: 3.4.22 and 3.4.23.

It prevents one to use any other merge tool.

This can be observed for different repositories, so it seems that some internal sourcetree configuration blocks / overwrites the selection.

Has some on an idea how to fix that issue?