Sounds like one of those weird unexplained crop circles you read about all the time Just kidding buddy
OK.....this distortion or dimple appearance is probably caused by the pvb effects that screenman stated. I've experienced this before when working on older shields where the lamination will separate just enough to allow resin to seep outside the damaged area. The ripples or waves may be caused by creating small little stretch marks to this very fragile pvb. When working on these you might want to start your repairs with less injection pressure and work your way up to get legs filled.
If this happens working with a new shield then something else is going on.
StarQuest and Screenman your ideas make sense. I'm going on that assumption and watch pressure especially on hot days as this problem as I recall has been in high 80's, guess I need to be sure and cool down some more.
Just kidding buddy 
