If needed, relocate the stock to obtain uniform pressure on its full length. Stock should be glued as soon after machining as possible. Too much time between machining and gluing. Panel shows evidence of steaming or burning. Check the curing cycle length.
Soft woods tend to burn when edge pressure is too high.
If the number of glue lines has been reduced, reduce the power accordingly. Check for proper glue mixture and storage and assure that the proper type of glue is being used. RF voltage could be too high at work. Curing time too long. A reduced number of glue lines.