You can read here for the new bugs that blizz is already officially acknowledging, but to summarize a few here:
-Players disconnecting from the game upon death in Alterac Valley (might be fixed now)
-Wrong item model for several tier 3 belts (Frostfire, Dreamwalker, Dreadnaught)
-Incorrect icons on certain items (AQR)
-Incorrect spell animations for various spells (some using wotlk or retail animations)
They might seem trivial on the surface to someone that doesn’t value what era is intended to be the recreation of, but the fact is that they’re all NEW bugs being introduced that era never had before. This is only happening because of SoD bleeding into era’s game version.