So after all this you don't have another scope and mounts to try.
the first thing that needs ruling out.
I have shot good groups then bad with my 97 but it was normally a gun fit problem the kt stock didn't suit my face.
Am older sporter stock was better.
Are you squishing your face into the gun to use small or medium mounts if you have some high ones you might find a more natural repeatable head position.
Scorpion. 177 hornet. 177 txhc. 177 s200. 177 97. 177 99.177 95. 22 80. 22 vulcan. 22 excorcet. 22
Trying hard to keep it down to 10 rifles.