Dough is too soft, causing the layers to stick together
Dough should be cool and firm when it is rolled out.
Egg wash has gotten on the edges of the dough
When using egg wash, only wash the tops of the puff pastry. If egg wash gets on the edges, the dough can stick together preventing the proper rise.
Product is old and out of date
Dispose of out of date products.
Hot filling has been placed on the dough
Cool fillings prior to placing on puff pastry dough. Hot fillings can cause the fat in the dough to melt thereby sealing the layers of the dough together.
Puff pastry is under baked
Follow package directions for proper oven settings and proper baking times. Check oven for accuracy using an oven thermometer.
Dough is rolled too thin
Carefully roll dough.
Dough has dried out while working with it.
Keep dough covered at all times. Dough should not be left uncovered for longer than 15 minutes.