It’s hard to know for sure.
Either the cards were designed differently on purpose, were accidentally missing portions of the white layer, or the problem was caused by issues with ink layer thickness and opacity (i.e., thin ink or less opaque ink would lead to holo bleeding through the CYMK ink layer).
The only reason that I mentioned ink thickness and opacity is because we have that exact problem on the opposite end of the spectrum (i.e., mirror/no shimmer/no sparkle holos).
It’s more prominent on certain cards because more of the background is non-holo (i.e., with a white core layer). So when that background turns holo, it’s more dramatic.