Mike and Sid,
My understanding is the ILF dovetail assembly should not be subject to any major forces at brace or during the draw. On Martin's riser the ILF fitting from the limb has been bearing on the bottom of the ILF slot as shown.
Mike, as you say, if the limb bolts are way out there could be a gap between the bearing surface on the limb bolt and the top of the slot at the bottom of the limb butt. I have seen limbs that had the slot cut too deep which also causes the ILF fitting to take all the inward (toward the handle) forces. This may be Martin's problem. Or the Riser could be out with the ILF slot to Limb bolt distance too long.
Martin, Please check different sets of limbs on your riser. There should normally be a tiny gap between the ILF slot and the ILF fitting. Whereas you should be able to feel a solid connection between the slot of the limb butt and the limb bolt.
Rasyad