Just noting that there are compatibility issues reported between block_mrbs and the latest versions of Moodle. I've not had any time set aside to look at this, but I wouldn't expect there to be a huge amount of work required to make it compatible (although, ideally, it could do with a more thorough review and add support for the privacy API).
If anyone wanted to take on the upgrade process and open a pull request to integrate it (or if someone had a budget available to pay for the update of the plugin), then I'm sure it could be fixed.