Have the fixed the Sneak bug where if you have level 4 or 5 of the first Sneak Perk, it resets to 1 once you go over 100?

You can go over 100? That's never happend to me nor has my 5/5 reset once I got there, on three characters...

Edit;Also, wrong section!

my sneak works fine and it's at 100 with all perks taken

Why should your Sneak level go over 100 in the first place?
There's no benefit to that, and it is only perks that help you sneak better. The level of the skill only functions as an unlocker of perks, sadly.

If you can get over 100, that's the bug.

I'm quite sure that's not true.. The higher my sneak skill got the harder it was to get detected even though I didn't invest in the detection perk beyond the first one which i unlocked from the start of the game...

I remember hearing about this issue. I don't know if it's fixed or not.

Basically, if you get enough stealth enhancement via perks or whatever else, it was possible to overflow the stealth value and it would act like you had 1 stealth.

I never heard of a sneak bug like this before, but I do know that the game can sometimes mess up the display of a skill, a display bug. Any skill can then drop to i.e. 25 on the skills page while it really is 100.

I have seen this display bug myself and only once. A reload of a previous save file fixed it, but I also read that the next level-up will fix it, too.

The only thing like this I have heard of is with the pickpocket skill. I haven't picked a pocket for a while, though. I recall seeing the chance of success displayed when you are looking in a Mark's pocket at a particular item, actually go down when donning enough pickpocket enchanted gear. Never heard of anything like that for sneak, though.