"Transfer failed: Timed out waiting for instrument response." on Linux with Analog Rytm mkI

I am unable to transfer files to my Analog Rytm MKI from Linux. Here's what I'm seeing:

Connected AR directly to computer via USB (the official red cable from Elektron FWIW).
Power cycled the AR.
On the AR, in Settings > MIDI Config > Port Config screen, set both Input From and Output To to USB.
Refreshed elk-herd app in Chrome. The app correctly recognizes the AR and its OS version.
Clicked "Manage Your Analog Rytm".
Selected +Drive / incoming (don't know if that's necessary).
On the AR navigated to [Global] Samples / incoming
Clicked "Send Sample File" and selected a wav file.
Pop-up in Chrome says "Sending" and displays a progress bar. On the AR I can see the filename inside the incoming directory along with a progress bar.
After a short time an error pop-up appears in Chrome: "Transfer failed: Timed out waiting for instrument response." On the AR the file no longer appears in the incoming dir.
After a short time the error pop-up disappears. The filename is listed in a right-hand column of the "+Drive" section. If I click "Scan +Drive" the file disappears.

Computer: Lenovo X1 Yoga, Linux Debian 10 (stable) Browser: Chrome Version 78.0.3904.97 (Official Build) (64-bit) Device: Analog Rytm MKI, OS 1.50

If the elk-herd app printed out logs or other debugging info I'd be happy to include that but it doesn't seem to.

Thanks for all your work on this! It'd be really neat to be able to use my AR without having to run Windoze in a VM.

mzero / elk-herd-project