Hi, I have a very stubborn problem with my S23. 

A while ago I boughT a USB to aux adapter for in the car (ugreen), worked perfectly for a while until recently. 
The cable sometimes connected and sometimes it didn't. When it didn't the usb logo kept popping up and dissapearing on top of the screen. Eventually it stopped working completely.
I figured it might have been the adapter so I bought a new one.  When I tried it unfortuantly the new one also didn't work. Over the last days I tested/concluded the following:

-Both USB to Aux adapters work fine, I tested them on/with other devices
-The aux cable works fine, I also tried different aux cables
-I tried the clear data/cache from the USB connection and then a reboot. This actually helped a few times, music played perfectly fine for a while, I even moved/wiggled the adapter/cable a bit to see if maybe it's a bad usb connection but it kept playing steadily. Until I disconnected the cable, reconnected and the whole problem started again. 
- I tried resetting all settings
-I tried the USB debug setting

None of this fixed the problem permanently, the frustrating part is is that it sometimes (very rarely) works perfectly so It can't really be a hardware problem, or can it? 
The issue seems to be that the USB connection rapidly turns on and off. Connecting to a pc/laptop is fine, charging; also fine. What is going on?