CRC error with Sony STR-DH550 about ipod-gadget HOT 3 OPEN

Looks like a USB/HID packet is lost. Could be hardware or software bug/problem.

• what is your gadget side hardware?
• logs from dmesg might help

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I use Raspberry PI Zero W with custom kernel 4.14.37+. Are there some specific things you'd need to know?

You can find the relevant part of dmesg log (kern.log) from https://pastebin.com/RTvyqTdt
The log starts when I loaded the first (audio) module. I then let it run so that the CRC error came 3 times, then I stopped the ipod userspace program.

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I tried this again with the latest version of the driver and the "ipod" userspace program, and now there is no CRC errors anymore and the gadget is detected by the amplifier.

However, I cannot get the speaker-test to work, running

speaker-test -D hw:CARD=iPodUSB,DEV=0 -c 2 -r 44100

seems to run for about 10 seconds but no sound is heard. After that, it dies with last messages:

0 - Front Left
Write error: -5,Input/output error
xrun_recovery failed: -5,Input/output error
Transfer failed: Input/output error

Any hints on what might be the issue?

EDIT2: Realized I can attach the trace file instead of using pastebin, here it is:
ipod.trace.log

Also I noticed that using any the amplifier's OSD to navigate the contents (with the default "ipod" userspace app) the amplifier hangs when selecting anything (like artists). I assume this is a limitation of the userspace app?

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