There is a little bug in the software of the Arduino Spot Welder. Once the weld counter reaches 10.000 welds the display gets corrupted. This was fixed in V3.2.3.
The problem seems to be caused by the variable types and convertings used in the program. For now to solve this issue in V3.2.3 the weld counter simply does automatically reset to zero after 9999 welds. For future software versions i will try to find a solution so the counter can count to values over 10.000 reliably.
You can find a tutorial how to update the Spot Welder Software here: Software Update Tutorial (just use new V3.2.3 instead of 3.2.2 used in the tutorial)
V3.2.3 of the Software can be found here: Github Page
Solution for the problem without doing a software update
In the older software versions you can solve the display problem by doing a “Full Reset” in the system menu. This way you manually reset the weld counter to 0. Then you can do 9999 welds before the problem occurs again. An instruction how to use the system menu is in the Quick Start Guide