I have a similar problem that I posted to the ASI Air user feedback - no response yet. I have since been more thorough in my testing, and corrected an error. Problem appears to be isolated to the camera, not the ASI Air+.
https://bbs.astronomy-imaging-camera.com/d/8149-asiair-user-feedback/273 - post #402
Connection issues with ASI Air + with main camera when powered.
I've tried several connection methods, and swapped many different cables, and where possible, swapped USB3 for USB2 just to see if I can achieve stable connection. None of the techniques have worked, so I'm making this post.
Everything connects easily and seems to be stable if the 1600mm is not connected to DC power. Focuser runs, filter wheel turns, Goto via EQMOD for the mount works. When DC power to the 1600mm is connected - the ASI AIR+ drops connection to that camera (and nothing else - unless using the built in USB hub - when using that hub connection to everything plugged into the camera drops)
I have tried using a powered USB3 hub instead of the USB hub on the camera - no change. I have tried using the USB ports on the ASI AIr+ without the focuser - no change. I have swapped many different cables USB2 & 3, different lengths. I have used the DC power from the ASI Air+ - no change. Direct power to the camera - no change.
Similar behavior when I connect to my PC (Windows10) and ASI Studio.
Suggestions, experiences, and help would be greatly appreciated.
ASI 1600mm Pro(main)
ASI 120mm Mini (guide)
ASI Air Plus
ASI EAF focuser
ZWO EFW (7)
Skywatcher EQ6r-pro (EQMOD)
Samsung Galaxy Tab A / Google Pixel 4a