you need a new battery and a new alternator/voltage regulator... i bet you, that the collective knowledge of this forum has this problem nailed better than the GTS motors... if the elbow on your suspension is oriented correctly (you checked it, right?), then the electrical gremlins are related to fluctuating voltage in the system... the GM, while responsible for many things in the car, will not affect the systems in this particular fashion...

banging on the driveshaft may have resulted in dislodging some of the contacts - the temp sensor, the oil temp sensor, a speed sensor in the hub that the work has been performed... especially the speed sensor can be responsible for the trifeca lights, the engine failsafe and the trans failsafe - when the system does not receive correct info about the rotational speed of a wheel, the system can't match the engine revs with the tranny revs, then one goes into failsafe and the other one does the same to protect the more expensive systems...

nav flickering could be due to mixed telegrams on the iBus, canbus but more likely related to voltage in the system...

check the speed sensor in the wheel that the work was done at, see if that thing is operational... take the V-meter to the plug at the ABS module (responsible for the tire pressure, the steering angle, the tranny matching the engine revs, the brakes) and see if you have good hall sensors on all 4 corners... let us know if you need help in the pinout of the ABS plug... for pinout will need month and year of production