BMW stalling with warning "maximum drivetrain output not available"?

So about 3 days ago my fiancés car randomly started to stall and then die while she was driving and the dash said the maximum drivetrain error as stated above. We turned the car off and back on and continued our day and there were no issues. Put my obd2 on it and the only code it came up with was a secondary code and that was 420665 shift paddle signal invalid. I thought maybe the clock spring but the horn works, cruise control works and all the steering buttons work. Car has done it every day once since the first time. The car is driven for about an hour before the stalling happened. Yesterday I replaced the spark plugs because I don't think they've ever been touched in hopes that it would fix the issue, but it did not. They are OEM NGK iridium's. Coils looked fine but in time ill replace those too. Today we were parked and idling and the rpms went haywire for a second and then the car stalled but all lights stayed on. None of the dash lights flickered.

What should my next step be for this and what could it be?

Thank you in advance!