Looks like you have 2 fields with the same DisplayName. JRiver 26 doesn't allow that to happen anymore when creating a new field, but if you created it on an earlier version, then it's there.
I assumed field Name and displayName were always unique. This causes MCratings to error out while loading fields, and only keep those loaded until reaching the error.
I have it fixed already in code, will release it next weekend. Meanwhile, you can hunt for your duplicate name. Suggestion: "show only user fields".