Book 12 that could break your computer or the game. However, there are a couple known issues that are good to know about, in case you happen to encounter them.
For instance, one such issue deals with the newly implemented cosmetic systems. If you happen to get your hair cut at a barber, you'll find that while your avatar itself will reflect the new trim immediately -- your character window will not. At least, not until your next login. This is mostly the type of issue that's just confusing more than anything else, but at least now you know that you're not going crazy from playing all the new content.
There are several other minor issues, which are all worth glancing at just in case you're encountering some new quirks during your time in-world.