TM:
Many years ago I had a similar experience, the only differences being that the veneer was butternut, and that the condition occurred before any finish was applied.
There was much debate about what the cause might be, everything from moisture problems, improper glue application, lack of pressing pressure, and that the veneer had been cut with a dull knife.
The fact that you are having these problems with products from two different suppliers leads one to think that the problems are post-veneer application; but I would wonder if the two suppliers used the same veneer source.
At the time, I maintained that the veneer had been poorly cut due to a dull knife, and that the back face was not flat, that the checks created by a dull knife created tiny waves on the back of the veneer that did not glue flat when pressed. I believe these checks manifested themselves when the moisture increased, in my case because of shop humidity, in your case when finish was applied.
I'm sure someone with more veneer experience than I will chime in to say how bogus this belief is. Perhaps when they do, they will offer a more plausible hypothesis.
As opinions are exactly that, the real culprit was never determined, but everyone agreed on the solution, which was to sand the veneer flat, apply a glue size to the face, let it dry, sand and finish. It seemed to work, as there was no callback.
Good luck with this.