I've been experimenting in Daggerfall. I took Alteration to 100. I was level 6 when I finished. I went to level Destruction. 20 skill levels later, and I'm still level 6. That's 20 skill levels on top of the excess Alteration it took to get from mid 90s to 100. Alteration was a primary skill. Destruction a major. I reloaded and tried Restoration, a minor. No good. I reload after gaining level 6 but before capping Alteration at 100, and I've gained two levels since while working on Destruction. For one's final level, is it necessary to go from 99 to 100 in every skill at once, in one action period, before resting to finalize it? If so, I've got some planning to do. That'll be quite a feat of micromanaging. Prolly have to get every skill one use from leveling, via tons of saves, but I can't let the game gyp me on levels.

(version 1.07.213)

I find it easiest to get the 6 skills all to 99 and then 100 all at once.

I have had a problem when 1 skill reached 100. I could not get any other skill over 95 until I enchanted an item "enhancing" that 1 skill.

(I have never had a problem with leveling up).