When starting a new torrent which has a single file i used to rename the file, click start and everything worked as i wanted it to work.
Now i rename the file, but the title remains the same, i click start and the torrent is inserted with the title and file not renamed.

I tried this in both Windows and Linux and both renamed the file correctly.
How are you loading the torrent?
When/where are you trying to rename the file?

I do it with auto load from watched folder.
It works if i rename the torrent title, but it doesnt work if i rename the file. it used to work with file rename if the torrent had only 1 file.

I see what your talking about now.
You can only rename the torrent name of a single file torrent, not the file name.

Thanks for reporting this

It should work correctly in v3.24.

If not, please let us know.