Ok well could do with a close up picture of the little white switches on the drives.

Also if you turn each axis screw one revolution how far does it move.?

Big problem could be the Laptop. Mach 3 doesn't support Laptops when used with parallel port and they are a known cause of problems.
My advise is to try a normal computer first before doing anything else. Other option is to dump the parallel port and invest in a external motion control card but won't get into that just yet.!!

Who setup the machine and converted it.? . . . 8.5Nm nema 34 motors is massive overkill for this machine and it's actually reducing performance not increasing. This is a common error due to thinking bigger is better but it's really not in most cases and unless correctly matched regards Voltage etc then they actually reduce performance and waste money.!!