Variation in Conti GP5000 sizing?

[enkei]

I must have fitted 3 or 4 pairs of 25mm Continental GP5000 tires without any trouble whatsoever. On different brands of 622x15c rim, they went on without struggle or complaint. Older GP4000 also went on without trouble.

However, the most recent set, bought a month ago, are probably the worst I've ever had in terms of the challenge I had to get them fitted.

Has anyone else found such a big difference in tolerance between tires that are ostensibly the same make, model, and size?

[SPINMAN]

I've been riding on GP4000 23c on both wheels with no problems. Then I went to Vittoria 23c and then GP 5000 25c on the rear. Now I swapped 25c to the front and GP5000 28c on the rear. Never had a problem on the same rims.