Replacing the 40 pin connector stops short of even "just the absolute bare essentials" of what these boards need to be reliable. All of the header connectors on all the boards need to at minimum be re-soldered, because most of them will have developed cracked joints over the years. Some may need replacing.

There are other very common problems on these boards such as bad original sockets (if it says SCANBE it's trash) and other problems.

Strongly suggest you go back to the guide you were linked to earlier and spend some time absorbing it.

These games can be made reliable, but it does take some understanding of why they fail, and some work put towards eliminating those failure points.

Richard