Error message when changing riskLevelRules

[Laurens Vets]

I have the following riskLevelRules:

"riskLevelRules": [
        {
                "name": "Not WORK",
                "comment": "Checks whether the field is_work is true or false.",
                "rule": "is_work == false",
                "score": 20,
                "reason": "FORMAT('%s is not a WORK network!', sourceIPAddress)"
        },
        {
                "name": "MFA",
                "comment": "Checks whether MFA used or not.",
		"rule": "userIdentity:sessionContext:attributes:mfaAuthenticated == 
\"False\"",
                "score": 20,
                "reason": null
        },
        {
                "name": "MFA2",
                "comment": "Checks whether MFA used or not.",
                "rule": "additionalEventData:MFAUsed == \"No\"",
                "score": 20,
                "reason": null
        }
],
When I try to change the reason in the 2nd and 3rd from null to "No MFA 
used.", I get the error message: "Modified Sensor parser config but 
unable to save enrichment configuration: JSON.parse: unexpected end of 
data at line 1 column 1 of the JSON data" and the reason is reverted 
back to null. Changing other items in the above works fine.

Any idea what might be going on?