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.