Basically… the LPT parallel port, as far as Mach3 is concerned, has Input pins and Output pins (10-13 & 15 being Input pins and 1-9,14,16 & 17 being Output pins with pins 18-25 being Ground). Input pins cannot be used as Outputs and visa-versa.
Your equipment manufacturer should have an understanding of this and provide you with settings for Mach3 that are correct.
However, the world is not perfect so we make do…
I would disable the X,Y,Z Input Signals (specifying pins 7,8,9)
Also disable Output #1 (specifying pin 5)
Try it and see.
Tweakie.
(I have been using Mach3 for more than 10 years now and I am still learning

)