A lesson I learnt then when having a go at drum lamination, if at first it don't stick, add more glue and more clamps! I found the these things really have to be clamped up bloody tight, so theres no place for being soft and trying to be sympathetic to the wood, CLAMP IT UP! and things will go your way!
When cutting the bearing edge for my snare, I found a couple of places where the plies hadn't adhered well. (probably due to my experimental laying up process, wont be trying that again, see other post!)
Shown above The poor laminations revealed...
A hearty application of glue and some strong clamps soon resolves this issue! Problem solved!
A decent laying up method should avoid this issue, but its always possible, still I found if it does happen the problem can always be solved.