If it was re-pinned at some point in its history, the lug has probably come loose against the bottom of the barrel, as Hungry Horse stated. Obviously, tap pins out from small diam side to large side if there’s a difference, which there appears to be on this one. Be careful when removing the barrel from the stock. Better to do it upside down and tap the comb lightly on a bench and try to drop the barrel straight down in your hands. Resist the temptation to pry it up from the front. Easy to chip wood out at the tang by doing it this way. As stated, after it’s out, you can see what you’re dealing with.
Also, You may have to spread, glue and clamp that lock side front pin location since it has a crack present. It may eventually grow the crack and weaken the holding spot there long term, otherwise. Compressing a tapered piece of metal in the hole should open it up slightly when the barrels out so you can get glue down in the crack. Might want to work an alcohol rag sideways down in that crack before gluing to clean up any oil residue and dirt. If pins are slightly mushroomed, lightly file and soften the leading edge before you reinsert to prevent tear out. If holes are wallered out quite a bit, you might have to drill out the barrel lugs to the next size larger pin. Those are my thoughts. You can do it. ✅👍
