MXF OP1a Stereo Export Issue

After updating to Premiere 23.1 on Windows 10, the custom MXF OP1a export preset I use for broadcast is converting stereo audio tracks to mono.  Other presets seem to be working fine.  

The "Separate mono tracks" checkbox under the audio tab is checked; but it is grayed out, so I can't disable it to determine if that is what is causing the issue.  

All worked correctly prior to 23.1.