You can set “A” as the only source for recording, no trouble with this.
Your track will then record this only source in Stereo.
So when you play this, you should have your sound in both ears.
Now I just tested it, first on a current project, it was doing complete nonsense.
But the project had begun before the upgrade of firmware.
I started on a fresh set and it’s perfectly OK.
(I will have to identify the source of the mess on the first set though, what’s happening doesn’t make sense.)