Hi Rob,
If the stocks been off the action for a long time it could warp a bit, or a lot if it gets damp or hot.
The fore tips are the most susceptible being the thinest, if you can still get the bolts in without forcing it to much its probably somewhere near.
I've put a little washer between the stock and the action as a quick fix in the past.
If it's not catching too much someone that knows what there doing can probably sort it out, hopefully you
It's just what wood does especially if it's not seasoned properly
Good luck with it mate Martin