I think this is perfectly normal APS behaviour. The voltage changes depending on what parts of the car are switched on/off. I don't think we have enough info to alert on APS failure, or even know this may be an APS failure based on a simple voltage measurement. My guess has been that the different parts of the APS have different output settings, and the switchpack may have an involvement as well. It is presumably two DC-DC converters in one box (as they can be individually = enabled/disabled).
I=E2=80=99ve never really confirmed 100% what =E2=80=98inhibit APS=E2=80=99= means. I think that it just turns off the part of the APS affecting the = PEM (but leaves the car part on - in particular VMS and VDS, and OVMS).
That 12v battery alert is really intended to alert on little 12v = batteries failing. I don=E2=80=99t think it can apply to Roadster based = on reading the voltage on the 12v line powering OVMS.
Perhaps it would be appropriate to change the module's web page for a Roadster to report "12V bus" rather than "12V battery" voltage. I was seeing 11.4V and was getting ready to replace my 12V battery until I (1) calibrated OVMS (187.5 worked for me) and (2) read further to realize that this wasn't the true battery voltage. Ken