Just to clarify, I did monitor this and definitely was still interested in the outcome ^^
If you want to further experiment, you should be able to do connection testing without the actual printer being attached, just with the board. At least connecting should work. Depending on the firmware that is on that board supporting it or not, there was also a dry-run command built into at least mainline Marlin that would allow to print without printing and that should unearth any communication issues. Alternatively you could try streaming a file to SD, if there are communication issues that definitely will also unveal them, maybe even more so than printing. Could you post a picture of the controller board?
Also, just as a heads-up, make sure you update the firmware on the silent board, I remember seeing some posts on here that indicated some issues with one axes stopping to move all of a sudden during a print that if I remember correctly got fixed for everyone trying so far by a firmware upgrade.