Very possible that you are getting hot spots. If the thermometer is reading 170, it may be hotter in other parts of the box. 212 will damage wood and glue.
the 8 hours isn't the problem and not likely the grit either as I know of guys finishing veneers with 120 and glass is only 80.
Glue starved gets blamed for a lot of things that we can't explain. More often it is another problem all together. If you peel a perfectly good lamination apart (pretty easy to do) It will appear as there is no glue present..or very little.
BigJim