This is probably an old problem sadly known to many of us. Some history will explain it.
The original LPT chip was designed as a general purpose IO chip. It was adopted by IBM to drive a parallel port printer. But the chip had many other features, including a bidirectional archirtecture. This was used by more than just Mach, to do many things.
The chip was discontinued, so the LPT was lost. Some IO card mfrs saw an opportuntiy here, and made some PCI boards to drive a printer. But read my lips: to drive a printer. These PCI cards do not have the full bi-directional features as used by Mach and other specialist 'things'.
Sad, but I do not know of any PCI cards for LPT which will work properly. Hence we go to the Ethernet and an external engine.
Cheers
Roger