It's possible that if the boards were forced closed because of the dowels, and the dowels were not PERFECTLY aligned, the pressure from this misalignment might have been from the dowels fighting back.
With modern adhesives, there is absolutely no need for dowels or biscuits. As for alignment, I can do a much quicker and better job without the aid of them.
Tony B Retired woodworker, among other things.
"Strive for excellence and settle for completion" Tony B