Hey a family member had this exact same problem crop up and he was using factory ammo in a tikka.
I told him that you might need to take the bolt apart and give it a clean as mine had rust on the inside of the bolt body when it was new. So he did, and said it was absolutely filled with shit.
Problem solved, clean your gun properly. Will be interested to see what the cause of your problem is.
Also a lot to be said for lubing the locking lugs, a lot of people don't know you need to use it with stainless. I just use the blue marine? grease or copper cote if its handy
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