I have had two MacBooks work great and one work poorly with my Bullet. One of the working macs has Mojave, the other El Capitan. The mac that doesn’t work didn’t work with either High Sierra or Mojave.
The main guess I have remaining is that I have installed custom USB serial port drivers for a number of microcontrollers on the machine that is failing, so I’m wondering if the Bullet’s new software is somehow conflicting with one of those drivers.
I recommend trying another computer, and in the meantime, I’m going to try to track down how to diagnose USB serial driver conflicts.