Lock and trigger problem

[Nordnecker]

This rifle worked perfectly for years. Now, it won't hold at full cock. Both lock and set trigger asssembly work fine out of the stock. Each one works individually in the stock. I've adjusted everything on the triggers to no avail. I can't see any wood interfering with trigger bar or sear.  I can feel a little bit of play in the front trigger when the lock is in. I suspect the rear trigger bar might be pressing on the sear arm just enough to keep it from holding in the full cock notch.
What is the best fix? I'm a little hesitant to try and bend the sear arm. I suppose I could grind a little off the bottom of it.
Asking for help/ advice, please.
Thanks

[alacran]

Put some inletting black or a sharpie on the rear trigger bar. Cycle it with the trigger and the lock installed in the rifle. This will let you know where the sear is coming into contact with the trigger bar. File the top of the trigger bar, where the contact is. Trial and error here. File a small amount then try it.

[Ross Dillion]

Wood shrinks over time. Put some shims under your trigger plate and try again. Leather, popsicle sticks, modified washers, I’ve used them all. It’ll at least show you if that is the problem.

[rich pierce]

Wood shrinks over time. Put some shims under your trigger plate and try again. Leather, popsicle sticks, modified washers, I’ve used them all. It’ll at least show you if that is the problem.

I agree. Something as thin as Manila folder shim can make a difference. Plus it’s easy to try and test.

[Adrie luke]

Maybe the sear spring is not strong enough.
The little bit of play in the front trigger can also be caused by the sear spring.

[Nordnecker]

I had a few minutes to fiddle with the gun last evening. I tried shimming with some copper roof flashing. I ended up with two layers folded over at the front end of the trigger and one layer at the rear. Everything works as it should now. I was surprised that it took that much shimming to make it work.