Is this possibly a head space issue?

[oldfoneguy]

It sounds like your issue is in the bolt shroud cocking piece sear area. If the bolt is rotating no problem it's not a bolt lug or setback issue because then it would need a tap to raise the bolt handle. Have you had it out of the stock and cleaned and lubricated everything underneath? Your sear could be sticking up and putting pressure on the cocking piece. Completely clean the bolt raceway especially in the bolt shroud area. Remove the firing mechanism from the bolt disassemble clean and oil it. Also check the sear spring for petrified crud keeping the sear from pushing down all the way. - Bill