I have found a way to cheat.
Submitted by Έρικ Κωνσταντόπουλος
Link to original bug (#777922)
Description
Created attachment 344508 A video showing the bug in action.
First, grab a piece and click on the give-up button, and then "Give Up". Put the piece you grabbed on the right board, and grab it again. Finally, put it on the empty space on the left board.
Note that the time is still ticking, even though it seems to have stopped.
If you do it quickly enough, then yay the score is counted :D
I have installed this on Ubuntu 16.04.
Attachment 344508, "A video showing the bug in action.":
tetravex_bug
Version: 3.18.x