Hi Don,
Do you get the red box around any fields being displayed (so you know which property is causing the validation error)?
Does this happen on all of your customers environments, or just one (assuming they have at least Non-Prod and Prod)?
Are they using OOTB Case Details page?
Is there any scripting on the page?
What happens if you create a new Case Details page and use it to display cases? Do you still see the issue?
Is there anything in the browser Developer Console?
Nothing earth shattering in the suggestions above, but might provide some insight into the issue.
Good luck!
Regards,
Dave.
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Dave Ward
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