From long time user reports here, I take it as a fact that "the game" including all WGT installations is very sensitive against connection issues. Icon explained lately that Flash may have some issues in this direction... Thus there are a lot of failure sources between the players' PCs and WGT's servers, if not in the game itself. The growing number of reports like above supports the impression that said sensitivity may have become a growing importance for game interruptions.
AFAIK, the game's completion count demands by each player the completion of multiplayer games until the final step to the main menu of the game screen. Only A/S games are exempt from this rule. Then he will get a "+" in the completion list which presumably has 100 entries. Any failure to do so will result in a "-", dropping the completion score. A growing number of "unknown errors" would push these scores down, resulting in more yellow and red buttons.
As a cure, there has been proposed a series of Blitz games with a friend which are a quick way to gain new "+" counts, eventually pushing enough minusses out.