If you replace the wood, here’s a solution. Drill the holes and mount the bunks to get holes positions correctly. Once correct, remove the 1 ½” lag bolts and remove the bunk. Go to your local hobby store and buy a bottle of thin CA superglue (Zap!) is a common hubby brand. They make three types, you want the thin one that is like water. Go home, dribble a few drops in each lag bolt hole and let ’em sit for an hour. The glue will “kick” and harden the surrounding wood to a ridiculous level (this is why you need to run the lag bolts in to set the threads first, otherwise you will likely split the boards).
After an hour (or quicker if you also buy a bottle of “zip kicker” and spritz the hole to fire off the glue) remount and you can use loctite if you want and the bolts will not loosen again.
Don’t put the bolts in too quickly, or they will get bonded in and will destroy the wood if you have to remove them for any reason. (I remove mine one at a time in the winter to inspect the bottom, clean it, check for blisters and repair, etc…)
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