I have an interesting bug. Seams to have started with the latest patch since that's the big difference with characters.
I have a couple of steam accounts.....on one steam account before this new version for skyrim I got the steam achievement for getting all 11 perks for being a werewolf.
Since this last skyrim patch I cant do this with my other account. In fact I told some friends who use and don't use mods at all and not one of 4 of them where able to unlock the achievement for the werewolf perks either all other achievements still seam to be working so far.
Also another strangeness I have one character that became a vampire lord completed the dawn guard mission on the vampire side then joined and did the companions quests and became a werewolf.....seams that character still has the vampire lord transformation.....along with the werewolf transformation.
In addition the vampires still treat that character as a vampire and I get ambushed by the dawn guard still.
I can even still enter the soul cairne even though I was a vampire when I went into it before and as I understand it wont let me enter if I am not a vampire normally.
But that character seams to be considered a vampire still just not effected by sunlight, cant feed, don't need to feed, just interesting and weird.
So not sure if anyone has any tips on this...or what to do for it.