Have you tried DLTF QS36F/filename? Or even an option 4 after doing a WRKOBJ on the file? It’s been a LONG time since i’ve worked in the 36 environment, but that’s what I would try first.
before deleting the physical file, make sure you delete the logical file first
then do a dspobj/wrkobj of that file/s and from there you can delete it
hope this helps