[Effeff]

edited: The error confuses me. Unless I have made a mistake (which I cannot see), "index -1" can only occur if a team balance occurs when there is only 0 or 1 players total on both teams. This confuses me because I thought I made it impossible for a balance to occur unless there is at least 1 player on each team.

I need more information if you can:
Do you have bots on your server?
Do you know how many people are on when this error occurs?

Please try with the latest version on github called "skillautobalance-kento-rankme". And, do not use both "skillautobalance-kento-rankme" and "skillautobalance" plugins, you only need one.