So the changes I made earlier this month did not seem to fix the problem with statistics not recording correctly.
As of this morning I've implemented some more changes that should hopefully fix the problem.
The only visible change to you the player is that Global statistics are now updated just once a day instead of every 3 hours.
If after a few weeks with these changes, if it becomes clear that the statistics recording problem hasn't been fixed, I have another idea on what I can do but it will be a lot more work to implement so I want to see if it's absolutely necessary before beginning to work on it.
I hope that even with the slightly buggy statistics issue that you are all able to still have fun playing World of Solitaire :)