It could be from stress. If it is and it's completely relieved itself the eternabond will hold without a problem. If it continues to crack you should take it to a place that's well versed in fiberglass. Most marine repair places are used to fixing these kinds of problems. They'll most likely gouge and end drill the cracks before repairing them.
Grand Surveyor GS-280 Pushing a 2500 Mega-Cab CTD!
Gotta go campin!