Other than caps lock, I'm not sure what you mean.
Is it the name of the iproperty or the value you're having trouble with.
If the name exists in custom iproperty as lower case then Inventor will usually default to that even if you try to rename.
Try adding a parameter as uppercase in the fx dialogue and set to export this may force overwrite as uppercase.
Untick export and delete the parameter afterwards.
Hopefully this is what you meant
You may want to look into some add-ins. My previous company had one that could force iProperty capitalization, among other things.
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