I have always said that there is then one way to skin a cat and even more ways to repair a stock.
The one thing you never want to use is Wood Glue. The reason is wood glue sticks to things very good, but does not stick to itself very good. Also oil and solvents attack the glue and cause it to break down. We all use oil and solvents on our guns.
Epoxies work best, but you need to use the right type. Some dry to fast, get to hard and brittle or don't get hard enough.
I have been repairing stocks for almost 24 years and have found that Acraglas works the best. I also like Devcon 2 Ton Epoxy clear with the 30 min set time. Both of these are not effected by oils and solvents once they have cured.
Now to talk about the arsenal repair on the stock in this topic.
It is a basic, Drill, dowel, glue. It is a good repair but the parts were not clamped together very well when the repair was done or it has started to come apart with use.
You have three options.
#1 Leave as is
#2 Reinforce the old repair
#3 Completely redo the repair
#1 is the easiest, do nothing and hope that it holds.
#2 Not to hard, drill into the cracks from inside the stock, using epoxy and dowels. The crack can be filled with epoxy, mixed with sanding dust, but will still show.
#3 This will take a little more work. First the old repair will have to be removed. That is remove the dowels by drilling them out. Use a solvent to remove the glue and clean the area.
Once you have it cleaned and able to clamp the crack tight, with the crack clamped tight, drill into the stock from inside the action. Drill into the crack from the back of the tang cut toward the front. This will allow the epoxy to have a larger surface to hold. Work epoxy into the crack and fill the holes. Insert dowels (bamboo skewers work best) and clamp. You could then drill from inside the action (down) and insert dowels.
Now for the holes from the old repair. Once everything has cured drill into the holes insert dowels with epoxy. Once the epoxy has cured use a forstner bit to counter sink the top of the dowels. Then plug with cross grain plugs made with wood that closely matches the woof of the stock.
Then all that is left is to dress up the area and blend the finish.