Based on the reported data, OP has 18% negative games in total. This implies that out of 100 games he has issues related to behavior in 18 of those games, or 1 out of every 5 to 6 games.
The reason for your decline in behavior score is evident—you appear to engage in griefing or become toxic in those games, and the responsibility for this lies not with the system but with your behavior.
Based on the reported data, OP has 18% negative games in total. This implies that out of 100 games he has issues related to behavior in 18 of those games, or 1 out of every 5 to 6 games.
The reason for your decline in behavior score is evident—you appear to engage in griefing or become toxic in those games, and the responsibility for this lies not with the system but with your behavior.