I have been laminating 200g twill carbon onto 5mm plywood recently to make kayak footrests and vacing them using the EL2 epoxy and slow hardener.  Most of the time they come out perfectly and just what the customer wants but every so often the carbon does not bond to the wood in a corner.  I always make sure the wood and carbon are fully saturated and down properly but 1/10 this always happens to and is always on an edge at a corner.

Resin starvation through capillary action by the wood endgrain? If you do that under vacuum you suck all the resin into the wood.