Are you using all the inputs and outputs? and what is your routing like?

Super interested in picking up a digiface USB myself.

Sweet, im hoping to do a similar thing but will probably use 4 focusrite octopre dynamics to my daw then eventually back out to a small compact 32 channel board for stereo mixdown.

Please let us know how you get on if you test 32 inputs recording/monitoring at once, as thats the feature that interests me personally, the digiface usb seems like a bargain if it works as i expect.

I agree on both.
Class compliant would be amazing, even if it would just get the phones out working that would be a great addition, as I am often using the Digiface as a mobile dac and I would rather use my iPad than my Laptop.

See manual, up to three, need to be synched between each other using ADAT ports.

Depends on your mainboard and chipset.

With my mainboard I could connect even two UFX+ which have even more ports.

But at a certain point I had to isolate them between dedicated USB3 controller,
because some USB2 devices (ie. Bluetooth USB or USB hubs), seemed to misbehave.

A good board for the UFX+ was the Sonnet Allegro Pro PCIe with 4x USB3 controller.
Unfortunately not available anymore, maybe you find one on eBay.
Needs a PCIe x4 socket on your mainboard.

But maybe it runs already out of the box...

You could also try the Sonnet Allegro (without "Pro") to isolate at least one of the two if there are issues.

The drivers of those cards are very nice, they use MSI, message signalled interrupts, which is a better
scaling interrupt model which has advantages especially under load.

Win7 needs drivers (available) in Win10 these drivers are already included and should be tried 1st.

With 2 Devices i.e.
Digiface 1 - ADAT 4 OUT -> ADAT 4 IN - Digiface 2

With 3 Devices i.e.
Digiface 1 - ADAT 3 OUT -> ADAT 4 IN - Digiface 2
Digiface 1 - ADAT 4 OUT -> ADAT 4 IN - Digiface 3

You need to work then with 2 / 3 TM FX instances and can't route channels across TM FX instances.
Each TM FX instance is a routing entity of its own.

Alternatively use 2 RayDATs, which you could sync internally by a 3-pin cable which you connect between the internal plugs SYNC OUT on one card and SYNC IN on the other. The 3-pin cable is part of the delivery.