L-Twoo? If so, hopefully it comes with a better RD than the one they send with their 11 and 12-speed stuff.

I finally just up and replaced the RX (12-speed) rear derailleur with 105 and it's a night and day difference. Really weird to have a b-screw that actually does something and springs that aren't made of wet noodles. For anyone on a budget, the 11-speed 105 rear derailleur is $15 less and works perfectly with 12-speed:

Did you use the 12-speed 105 derailleur, or the 11-speed 105 derailleur? I understand that both should work (per your message and the video), but I'm curious about your specific data point since I'm also on L-Twoo RX.