I must be missing something really obvious, but I couldn't get a merge to complete this evening in Sourcetree 4.1.5 on macOS Monterey. There was a merge conflict in a source file, I launched the external merge editor, resolved conflicts, saved, and closed the external editor. Sourcetree showed the conflict as resolved, so I right-clicked on it in the file status box and selected "Continue Merge"...but it put me right back where I started, with the same conflicts in the same file! I tried it a couple times, and every time that I asked Sourcetree to continue the merge, it went back to the start.
In the end, the only way I could get it to continue was manually in the terminal, using "git add" and then "git commit". That worked perfectly and completed the merge.
Is there something I'm doing wrong?