"it is almost always possible to receive 485 on a PC by just using
GND and one side of your 75176 output to rec"

Almost!

So if you have a problem, where are you ALMOST going to look for the reason?

It is very bad practice to rely on something working without being up to snuff, if you are going to go 485 to PC at least use a converter.

Instead of fighting problems caused by not doing ot right, Have fun,

Erij