Some panels do take 23.976 but they don’t like the PsF nature of the signal. Is there a checkbox somewhere to make it straight “P” instead? The DX hardware finally added that support with last few versions of MC software.
Also, I don’t know for sure whether this falls into the “universal mastering” feature set of Symphony or not where 59.94 might be considered one of those rates. Are you on MC or Symphony when you see the issue?
I don’t have the same set-up so I can’t test to be sure.
Michael