Apple Lightning to USB 3 Camera Adapter does not work after iOS 12.4 update
After updating my iPhone to iOS 12.4, my Apple Lightning to USB 3 Camera Adapter is not working as previously. I use the adapter with an external portable USB DAC (AudioQuest DragonFly Cobalt) to play music files through headphones. This specific Apple adapter is recommended by AudioQuest for this purpose ("best sound quality"), and the adapter previously worked fine.
At the exact moment I updated my iPhone to iOS 12.4, the adapter stopped working properly. Now when I start to play a file, the adapter seems to be attempting (but failing) to draw power from the iPhone for the DAC. A music file starts to play, but then stops playing. Sometimes play will resume through the built-in iPhone speaker (but not through the DAC). If I connect a power source to the adapter's lightning port, the adapter will usually (but not always) allow files to play through the DAC (that is, it works after a fashion).
Importantly, other adapters/hardware configurations continue to work fine - Other lightning to USB adapters with my iPhone -- the older Apple lightning to USB 2 adapter (no simultaneous charging), third-party lightning to USB adapters, and using the DAC with a USB C adapter connected to my iPad (also iOS 12.4). Thus it appears to be a specific problem with the newest Apple lightning to USB adapter in this use case.
I have tried restarting my iPhone, various plugging/unplugging scenarios, and I have the latest drivers on both the adapter and the DAC. Any recommendations appreciated; it would help to know if others have experienced similar. I am contacting AudioQuest separately. Although I don't think the problem is with their hardware, it is conceivable that a DAC firmware revision would allow it to play better with the iOS 12.4/adapter configuration.
iPhone 7, iOS 12