Interesting. Yeah, I used my 2i4 for the update and to batch write all 99 new sounds.
I never had a problem with the MIDI I/O on the 2i4 with FI V2 or any MIDI-able device I use (Pigtronix Infinity, Akai samplers/drum machines, Korg KP3+, Roland synths). I do not know enough about software writing to understand why or how the 2i4 interface would previously work flawlessly but now be glitchy with new FI firmware/software, as nothing changed in the 2i4. Maybe this is also a bug to be fixed in future updates? To lose compatibility with a previous compatible device seems like an oversight. But what do I know; I'm a musician, not a software developer.
Also, Quatschmacher, thank you so much for fielding all these to-be-expected issues that happen with any major update! You should be on the PA payroll if you are not already.