Having the same issues currently. I have the anti-gravity battery and switched back to my factory motorcraft battery and am still having the same issue. Voltage just varies from 14.4 and will drop to 11.5 sometimes. This first happened to me tracking the car and now happens every time I...
The ring on the end of your half shaft needs to be seated correctly inside the rear diff housing. If it's not seated correctly it will leak. You will have to take off the caliper and lower control arm to access.
I have Apex SM-10's on Cup 2's and haven't had any problems, but I use PS4's on my stock rims and one keeps leaking air slowly. Tires are brand new and they've only been on for a month.