since the bit is not damaged, i am assuming that the guides/bulkheads of the lathe are misaligned.
Coming from an engineering background I would not say that the guides are NOT misaligned but perhaps looser than new. ( since you use the same guides for forward or reverse cutting I guess that the tool block is twisting in forwards or reverse)
Most comm lathes have two grub screws which push on to a slide clamp to adjust the slide tension.
Try tightening these up very slightly to remove the wear which will have occured during use.
They may have lock nuts on them to prevent them self ajusting in use.
Also - Check that the comm is turning in the correct direction so that the tool cuts rather than rubbing.
Then check that the tool is sitting at the correct height to cut.