pros-cli: Cannot upload binaries to V5 brain: couldn't find the response header in the device response

Expected Behavior:

Successful upload of binary to microcontroller.

Actual Behavior:

Uploading /Users/jeffrey/Documents/hello/bin/output.bin to v5 device on /dev/cu.usbmodem1421 as hello to slot 1
Uploading slot_1.bin (/Users/jeffrey/Documents/hello/bin/output.bin) [#-----------------------------------]   2%
ERROR - pros.cli.upload:upload - Couldn't find the response header in the device response. Got  but was expecting aa55
  File "/usr/local/Cellar/pros-cli/3.1.2/libexec/lib/python3.7/site-packages/pros/serial/devices/vex/vex_device.py", line 69, in _rx_packet
    raise IOError(f"Couldn't find the response header in the device response. "
OSError: Couldn't find the response header in the device response. Got  but was expecting aa55

Steps to reproduce:

1. prosv5 conductor new-project test-upload-mac
2. cd test-upload-mac
3. prosv5 make
4. prosv5 upload

System information:

Operating System: macOS High Sierra (10.13.6)

PROS Version: 3.1.2

Additional Information

I installed PROS 3 using the instructions for macOS installs involving Homebrew for the latest release (3.1.2). Uploading works fine on another computer running Windows 10.

The percentage at which prosv5 upload fails and outputs the above error message varies from about 0 to 25.

Screenshots/Output Dumps/Stack Traces

Full output of prosv5 --debug upload