Hi PAH, welcome to the Forum!
I'm not sure I can understand exactly what you're saying, but usually the inability to get focus at infinity with an M42 lens is due to the wrong type of adapter.
Are you sure the "original" adapter is in fact a genuine Pentax adapter? The type which works properly at infinity will look similar to the photos on this page:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/112710-best-m42-adaptor-3.html
You will see that the adapter fits flush into the camera body. In other words, there is no "
flange" which is wider than the aperture in the camera body.
I'm hoping your adapters are both of the flanged type, because this will explain your problem. If not, maybe there is a lens problem. What sort of lens is it?