Why switching from custom settings to default settings in Group Level failing?

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I have groups with over 50 projects and they are currently configured for Jira integration as custom settings but I want to change all to default settings. In the documentation written that this task could be done at an instance or group level. I am getting following error when I try to change at one of levels:

“Use custom settings” to “Use default settings” for projects which had Jira integration configured before I configured the Jira integration on instance level as default for all projects, I get this error: “Validations failed. Password can’t be blank”
same from here