We have seen that players are sometimes losing significant amounts of MMR after a match has ended, with no indication that it was a roll back from a cheater being banned.

Our team is currently investigating. As a precaution, we have deactivated the MMR Roll Back feature while we determine the root cause. For those of you curious about the intended functionality of the MMR Roll Back feature, you can learn more here.

We will update you further when we have more information.

UPDATE 1

We have found that the pop up to notify players their MMR is being rolled back is not triggering, and thus not being displayed when a roll back has occurred.

Additionally, matches that needed to be rolled back were not flagged as "complete" once the MMR was removed from players in that match. This lead to roll backs occurring multiple times for the same match, creating larger than intended losses.

UPDATE 2

We have confirmed that we have a record of all MMR lost due to this issue, and will be able to restore MMR to those impacted. We put together a script to do that today, but it came with additional risks that we were not comfortable with taking.

As such, we will discuss and work on a solution when our entire team is back in the office on Monday. An additional update will come on Monday when we have a more clear idea of our next steps!

UPDATE 3

We have restored MMR that was lost to all impacted players. We have also restored the uncertainty value to what it was prior to the massive MMR losses, so players will be able move through the ranks as originally intended.