Plans grinding to a halt. Now the Takumar SMC 300mm is having issues

This is a bear of a lens to use.  It is not the largest of the Pentax 6x7 line-up, but the most under planned lens.  When this lens is mounted, it is a huge 8 inch protrusion and the 82mm gape is hard to miss even at even 100 feet away.   This lens I got off ebay had an interesting story.  It was mounted to the outside of a helicopter a few years.  When I got it after auction, it was covered in gaffers tape and had some scratches where all over the barrel, but yet the optics looked clean.  It was a six hour job to clean and reset the off infinity set of the lens. Now I pick up the lens for a simple sight test and it looks like the infinity is off again.  How?  The repair would require the peeling off of the grip of the focus barrel to do the adjusting.  More later.