I can’t see it being the scope Jerry, I think it’s me for now. Will keep everybody updated.
The combined value of the scopes we have seen go down within our small group of F class shooters would buy a very nice car... and this includes all the biggest names in optics.
Assume nothing... test everything. Scopes wear out and/or break. This is the first place we check now cause it is not something you can readily see.
Obvious and visible things like fouling or a loose widget, you would have dealt with (I assume)... wind is a no brainer. Things like neck clearance/turning, annealing, load charge consistency, seating depth consistency, etc, etc.. assume you have already addressed. If not, plenty of areas to check.
for the rds it takes to confirm, swap scopes from another rifle and see what happens.
then the barrel gets a serious look. For true benchrest shooting, barrels will 'wear out' pretty quick... think hundreds of rds... not thousands of rds.
finally, firing pin spring and lube. With the cold, gunked up firing pins can cause all manner of woes. check the trigger too.
If the obvious visible parts work, move to the stuff that is hard to see....
when shooters put in the effort to shoot well, I don't see them having wild swings in shooting form and follow through... now if you have a physical disability, work with what you got. If you regularly shoot 1/3 MOA with a combo, then suddenly you are at 3/4 MOA... and then back to 1/3 MOA.. and then... You will know you have shot poorly. Asking this question here leads me to believe, stuff is happening that doesn't make any sense.
I have diagnosed a very expensive scope in 6 rds that was sent back for a complete over haul. I know the rifle, shot it before and it was superbly accurate. In those 6 rds, I couldn't tell you if the next shot was going up, down, left or right. Same load, low rd count on the barrel... wild on the target. Scope swap and it was driving inside the V bull on demand wind and all.
Eventually, something like $15,000 worth of scopes were sent back for a refresh/rebuild. We now treat scopes as a wear item.
YMMV
Jerry