Since I use TiteBond, and it swells the wood because it's water based, this always happens at the very tips of the fades as soon as I apply glue (takes only a few seconds). It will press flat when gluing so not a problem.
If the wood is thin enough to get wavy like that, it is thin enough to flatten out under pressure.
You can do a dry run to confirm.
Wood was probably dry when grinding, and now has absorbed a bit of moisture. Not a big deal.