Same here. My first post (six month ago) which described my problem with a usb-c audio adapter was never published... 

... As long as the phone is still in use, the OTG function will not be turned off. I want to confirm whether you have not used it after connecting to the OTG in 15 minutes? If the OTG option is disabled none of my audio converters are recognized and my BV9900Pro uses internal speakers. If I turn op...

Where can i find the OTG settings? I bought two USB-C audio adapter and both do not work. Only chance to get them run is to enable the the OTG option in Smart Assist settings. But this is not the solution. If I the option is unchecked no audio adapter works. If I check it I can listen music for 15 ...

Where can i find the OTG settings? I bought two USB-C audio adapter and both do not work. Only chance to get them run is to enable the the OTG option in Smart Assist settings. But this is not the solution. If I the option is unchecked no audio adapter works. If I check it I can listen music for 15 m...