Here's what I remember about Abyss problems back when it still worked:
Item Hooks completely down, been down for a while, don't expect a fix but it's broken. Very useful mods.
Multi-client prevents switching between window and fullscreen mode. If I start fullscreen, the second client must also be fullscreen, or otherwise does not open. If I open second client fullscreen, then switch either client to window and change windows, it turns grey. Cannot access other windows either, as the grey stays on top of everything. Can be fixed relatively easily by switching the window client back to fullscreen.
Also multi-client, sometimes if I do not stay on the same window while the world loads, it freezes and turns grey.
Another problem, commonly while multi-clienting, and it crashes, I cannot log on to the same character after reopening. Have to first log on to another character, log off, and switch to the character that crashed. Usually takes a few tries.
There was a slash command that crashes client, can't remember which.
Right clicking to toggle mods usually doesn't work.
As of recently, and I did report a few pages prior, Abyss completely stopped working. If I open via Direct Launch, Mabi is stuck to a completely white screen. Opening through client does not work at all, meaning I cannot open, gives error and closes. No reply so far, I have no idea why. Was told (by someone ingame) something about race.xml or something, but unfortunately, I cannot find where that was located in Abyss. Rather... I thought that was a Win 10 fix...
I'm on Windows 8.1 (Boot Camp), 13" rMBP.