Hi Shelby,
We have checked with the provided information and the issue “MonthInlineAppointment always null for custom events” is not exists in our latest version (16.1.0.32). We have prepared a simple sample with custom appointment. Kindly find the sample below,
Could you please check with the provided sample and revert us whether issue prevails? Else, kindly modify the provided sample with issue replication procedure. So that it will be helpful for us to analyze and provide you better solution.
Regards,
Ganeshamoorthy C