Did you look at the System Report? There can be multiple ports on the same USB Bus and I would not be surprised if your MacBook Air only has a single USB Bus. That means data collisions are inevitable, resulting in the interruptions you are seeing hearing.  Thanks! I'm actually working on an iMac with two USB busses, so your comment about the same bus gave me an idea: I put all the docks (I've been calling them caddies) on the USB-C bus, and the DAC on the USB 3 bus. It worked. No more drop outs. 
iMac (19,1, 3.1 GHz i5, 12.7.4, 40 Gb RAM); MacBook Air (1.8 Ghz, 8 Gb RAM, 10.14.6, 256 Gb SSD) Vodafone router and Devolo Wi-Fi Extender, Canon TS8351 printer/scanner.
| 
