Date format issue in RTF format

Summary: We're trying to pass the date period filter criteria to the RTF template as MMM-YYYY, but it keeps coming our as a five digit number. Documentation reflects that <?format-date:P_START_PERIOD; 'MMM-yyyy'?>  should work, but it isn't for us. We've also tried 'Mon-yyyy' and other variations.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable): 24A

Code Snippet (add any code snippets that support your topic, if applicable): <?format-date:P_START_PERIOD; 'MMM-yyyy'?>