Here is an article describing a fix that you could try in case of problems when working with a USB cable connection between a PC and Mountbatten Brailler.
If you encounter any problems with communication between Mountbatten Brailler or Mountbatten Braille Whisperer and MB-Comm software through USB cable (connection errors, missing letters or whole words during embossing), please select an option “Safe USB transfer” in connection settings. This setting will be stored and you won’t need to change it in the future.
select “Connect Mountbatten” from menu “Device”
click button “Settings” in displayed dialog box
in displayed window check “Safe USB transfer” option in section “Advanced settings”
confirm this settings with “OK” button.
The following screenshots show described steps: