A reduced number of glue lines. Edge pressure too high. Improper glue mixture. Mineral content of wood. Improper glue spread.
Panels show evidence of crushing along joints.
The moisture content should be within tolerance. The problem may be occuring due to occasional pieces of stock with high moisture content. Moisture content too high. Panels show evidence of crushing at the corners next to the shoes. Isolate the questionable shoe or rearrange the stock so as to distribute more evenly the entire length of the panel.