A bit hard to describe (or it's just too late here), so here's how to replicate it:
1)Go to hangar, select any plane, and select a non-default skin for that plane
2)Then select a plane which you don't have enough perk points for (in my case this is only the 262, I don't know if it applies to other perked planes or not)
3)Return to the plane you selected in step #1, and you will see that the skin for it has been reset to the default.
I noticed this a week or two ago, but I forgot about it until I didn't see it in the latest release notes.
