Another way to do this, is simply to export the ones that are incorrect. Assuming you prefer “Residential” instead of “residential”, just create a Segment where the custom property = “residential.” Then, export this Segment with this one field selected In Google Sheets, change the field values to “Residential” export the CSV and then import that as a CSV back into Klaviyo.
You can keep this Segment around in case more profiles have “residential” and you can keep an eye on this Segment periodically.
Separately, you should try to audit your systems to see where the origin of the bad data is coming from. If it’s coming from an integration, a Signup Form, Flow Action, or from other external tools or imports, make sure to fix it at the root problem to mitigate bad properties from happening in the first place.
If there’s no way to easily resolve the root issue, you can consider using a Segment Triggered Flow with a Update Custom Property Action that updates the value from “Residential” to “residential” to automatically update this value whenever it occurs. Just note, Segment Triggered Flows can occur only once per Profile.