You are able to get wrong results in the commit searchbox if you check "Current branch" checkbox white search is still performed:

1. Type some text for search which is present in commits in the current branch and in another branch
2. Hit Enter to start search
3. Check the "Current branch" checkbox
4. The results after hitting checkbox may be overridden by the results of the search started at point 2:
   

(This screenshot from version 2026.04, but it seems that bug is still present, because I didn't found any commits that may fix it)