I confirmed that you are telling. The point was “delete playing track” (as you said).
When a playing track is deleted, TuneBrowser lose playback position and place playback position into -1 (it means “before top of the playlist”). And playback continues while possible. When playback has finished, playback position will be incremented from -1 to 0. This “0” is the top of the playlist.
This behavior is according to the basic operating policy of the TuneBrowser. And also I think this is not proper behavior for the case you are explaining, but I cannot figure out now what shoud I do while keeping the basic policy.
I’m sorry but I did not reach a conclusion.