1. There seem to be ways to leave the ranked game in progress without being affected with a loss in the "ELO rating".
  2. A lot of abuse in leaving the game early so the partner gets full ELO boost.
  3. The way the ELO scoring works need to be reviewed in full.
  4. You can easily spot cheaters on the daily records page eg: https://worldofcardgames.com/spadesDailyRecords.html