I've read of both issues elsewhere. Sucks because there aren't great options no matter how you cut it unless you're really willing to dump some cash.
What I find most odd is that when I finished the x-carriage prints I test fit it with wheels that didn't come with the i3 Plus, they were a set that FLSun had sent me separately for my other i3, and it seemed pretty smooth. I ended up just putting those wheels with the others for assembly and now have carriages that aren't a smooth as before.
Going to have to build a little test rig and just select the best 9 out of what I have and hope for the best. Ordered a lot of PA wheels as well, see if they're any better. Not ready to give up on this, just need to design around it.