I won't say it's uncommon for this to occur, but I am surprised given the quality of the manufacturer in this case. LMT isn't a cheap, lower shelf model.
All the folks above have given good info. I am with Jpyle that you might want to check the spring tension on the rear detent.
Your rear take down pin should require you to clamp down on the upper and to firmly press it out. It definitely should not be "easy" or "light pressure" to just pull it out.
The Accu-wedge is a great product and will serve you well. Be careful. You will IMMEDIATELY encounter people that will give you all sorts of Interwebz BS about how the Accu-Wedge is going to immediately come apart during your first real shooting session, the parts will tumble down into the trigger mech and leave you dead in a ditch.
DO NOT listen to these people. The Accu-Wedge is a very good product and if you just look at it for wear when you clean the weapon, you will see IF it gets to the point of actually seeing wear.
For what it's worth I have seen them get discolored from use, but I have NEVER seen one disintegrate into pieces and lock up a weapon.
If this rubberized wonder is somehow demonized beyond belief in your personal shooting circle, there is another option.
JP Enterprises make "Anti-Walk" pins for the FCG and the Pivot and Take Down pins. Once you install these, "field" stripping becomes a PITA because you need the tools to disassemble them, but it will be a more "steel" solution to your problem.
Personally I like the Accu-Wedge if your rifle experiences this minor issue.