Hi Chris,
We understand you are using modern experience in your list, please try switching to classic experience, try editing the list, check if you still get the same error. To switch, click Return to classic SharePoint at the bottom-left corner of the page.
Once you are in classic experience, select the List tab on the ribbon and click Quick Edit, now try editing the list, check if you get the same issue.
Besides, please try opening browser in InPrivate mode and check if you get the same issue. You can also try another browser in InPrivate mode and check the result.
If the issue persists, please check with the other members of the site to confirm if they see the same behavior.
Regards,
Neha