A lot of "Access denied" errors after upgrade 10.11.6 to 10.11.7 on windows

We are using MariaDB since ages on our servers and always upgrade every major and minor version.

After the last upgrade, many errors pop up in the error log, but the errros seems not to happen at application level, as we cannot identify issues in the applications itself.

The errors seems to be only in the error log, without ever really happen. We came to this conclusion, because some of the errors shows users and databases that are not even in use. They exist, but no access to that databases happen.

We cannot identify where this errors come from, but they are here since the upgrade in all production servers that got this upgrade. They happen at random times and are impossible to reproduce, as everything seems to work fine.

Here is a set of this logs that happens in bursts just for almost all available users in the database at the same time, which is impossible that any app causes this at the exact same times.

All those users just work fine without ever touching the permissions of any. All apps still runs fine with this users, no matter how we access them.

We are out of ideas to debug this...