When manually typing at the keyboard, it's hard to tell if intermittent character loss is due to a bug, or because the keys were not pressed properly. This device solves the problem by emulating a USB keyboard and generating characters programmatically.
For more details on using this device and a schematic of the circuit, see the README in the GitHub repository.
I built this device using Vero board, but it could easily be built on a breadboard.
The code in repository has the configuration files to allow it to be imported into the PlatformIO development environment, alternatively it may be edited in the Arduino IDE. The code uses three libraries; Bounce2 to software debounce the buttons and switch, the Arduino TFT library to drive the display and the Ticker library to control character generation rate.