I have investigated this as much as possible however unfortunately I am missing some debugging logs due to the file size limit being reached.
Essentially what happens when you are given score:
myScore = oldScore + scoreGiven
Simple? But somehow myScore ends up as 0 afterwards, which makes zero sense. I am using the defualt SA:MP score system but have now made my own script-controlled system to keep track of score. Perhaps there is a rare SA-MP bug where your score is reset to 0 somehow.
I have also implemented the following:
If a player is given score, but their score afterwards is zero, it will revert your score back to what it was before. The change will be blocked and an error message will be logged.
Sorry for this issue.