Thanks for the reply! That is the case, and is a known issue that we are looking into currently.
For now, as a workaround, there is a UI Script you can use that will attempt to clear that field when editing a test run so you din’t have to make the change every time. Please note, this script is not officially supported, and has not been tested in larger environments, but anyone is free to use and make changes to it as needed.
name: Change Run Assignee
description: Changes the 'Assign To' value of a test run to blank to prevent re-assigning all tests to a single user when editing a test run.
var assignee_list = document.getElementById('assignedto_id');
assignee_list.options.selected = true;
If you are unsure how UI Scripts work within TestRail, you can learn more about them on our website here: