The new Beta 2 looks very stable and promising. Many thanks for the nice and good work.
I used it now for 2 hours without major issues. I only have a few suggestions, see below:

1st of all I describe my setup:
- 1 UFX+ (Guitar Rack), connected via USB3 to PC
- 1 UFX+ (Main Recording Platform), 2 Octamic XTC via MADI as AUX devices, also connected via USB3 to PC
   the 2 UFX+ connected to each other via ADAT1
- 2 TM FX instances, one for each UFX+
- ARC USB, connected via USB to PC this time

Thanks for adding the features
- to display volume changes on the UFX+ display, when the ARC USB is plugged to the PC
- to be able to select, for which recording device the ARC USB shall be working, if multiple are connected to the PC

I configured the ARC USB this way
- activated only for the UFX+ in the guitar rig
- key assignment:
    05 - SNAP5  -  Play Start/Pause
    06 - SNAP6  -  Play - Next File
    07 - SNAP7  -  Play - Previous File
    08 - SNAP8  -  Record Start
    12 - EXT Inp - Record/Play Stop

I am very satisfied with the functionality, that pushing the "record key" immediately starts a DURec recording
and that you need to push "stop" 2 times, to prevent stopping a record erraneously.

During test of the new functions some questions / wishes arose:

1. It would be very practical to open the Record/Playback screen for another 10 seconds
    when using one of the new 5 functions in the area of record/playback.
    Reason: after 90 seconds the Record/Playback screen vanishes and defaults to the channel overview

2. If you have one ARC USB for multiple devices, like the 2 UFX+, I would wish for a new ARC USB key command
    to be able to toggle, to which recording devices the ARC USB shall be active:
    ALL devices, device 1, [ device 2, device 3, device N ]
    Ideal would be if TotalMix FX dynamically detects, how many devices are valid for the ARC USB
    so that this toggle function automatically does the right thing.
    If there are 2 devices to toggle between: ALL, device 1, device2
    If there are 3 devices to toggle between: ALL, device 1, device2, device3

3. It looks to me that the ARC USB key settings currently are globally set in TotalMix FX.
     Possibly saved together with a workspace (only an assumption,
     as I think I lost the ARC USB key assignments when recalling a workspace)
    I think on the long run it would be better to be able to store the ARC USB key settings
    into perhaps also 8 slots (compareable to snapshots per workspace)
    AND that you save in a SNAPSHOT
    - the currently active ARC USB key assignment and
    - for which recording device the ARC USB connected to the PC shall be active.
    This could do wonderful things to you .. if you recall a workspace or snapshot
    as then you get also some flexibility with the ARC USB, how it shall behave exactly.

4. A suggestion to map the Windows "F4" key to open the "ARC and Key Commands..." Window
    If you are setting up the ARC USB, and trying things out, then this wish comes automatically

5. I wished for more consistency in terms of LED activity on the ARC USB, less "blink blink"
    For operations like Snapshot selection, MONO, MUTE, PLAY I would vote for steady light
    For operations like Record/Play STOP would use only one blink and then nothing ....
    For operations like Record I would use blinking light of the key which issues recording
    When I issue a DURec play or stop operation per ARC USB key command I do not understand
    why the SNAP1 key, which before was steadily lot, starts blinking and this in a very irregular rhythm.

    The following order of operation results into too much blinking, finally also an changing and kind of flickering blink,
    which does not look like "sane operation" of the ARC USB

The repeatable steps:
a) if you push key1 (SNAP1) then key1 is steadily lit, ok.
b) if you additionally push key9 (MONO), key1 and key 9 are steadily lit, ok.
c) if you push key5 (Play Start/Pause) then key5 and key9 are lit and key1 (SNAP1) blinks.
d) Why does SNAP1 blink? Is the status of Durec part of a snapshot so that is regarded as a change ?
e) Now 1 further.
    if you hit key12 (Record/Play Stop) then funny blinking starts.
    - key9 (MONO) is still steadily lit, thats fine and logic
f) But why does key1 and key5/12 blink alternating ?
    If I stop something by key12, then pause (key5) should be dark = not in effect anymore.
    And if DuRec is stopped, then I would expect that neither key5 nor key12 blink.
    Still the question why key1 (SNAP1) blinks in this case.
g) Besides this key 1, 5, 12 blink in a very fast sequence and very irregulary which looks a little bit "out of order".
    If I remove and re-plug the USB cable to the ARC USB then this status stays exactly the same.
    So this doesnt seem to be on the side of ARC USB, its the way TM FX triggers / controls the ARC USB.
    It doesnt make a difference whether I connect the ARC USB to an USB2 port or to an USB3 hub which is USB2 compatible.
    The irregulary flickering continues.
h) if I finally hit key-1 (SNAP1) then it is steadily lit again.
    But what now ? Now the key8 starts an hectic irregular blinking.
    Such irritating "blink - cascades / dependencies" should be avoided.

In regards to your answer in the other thread, Matthias, there is IMHO no double assignment of ARC USB keys,
as in one of the two TM FX instances I deactivated the ARC USB which is connected to the PC.