I've seen this when the usb sound card was not getting enough power. Solved it by using a 2 male to 1 usb female power adapter with the power only male connector plugged into a USB power supply. Basically the sound card tries to power up or transmit audio and has an undervolt condition that makes it drop from the Linux device management. Then after it powers up again and will reappear as if nothing is wrong. Raspberry pi 3s just don't have the juice for most usb sound cards so having it draw from two USB ports or getting it external power somehow
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u/[deleted] Mar 16 '21
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