Hi JR 47,
More than likely your fuel level sensor has failed or the float arm and float are sinking. I attached the process on how to replace the level sensor but it is part of the module so you may still have a part warranty on that part if you can take it back.
The way this works is the sensors gets a voltage signal off the position of the float arm and sends that to the cluster. When it fluctuates like this, it is as I said, either the arm is moving too much and the sensor is sending the voltage of the arm or the sensor is incorrect.
Images (Click to enlarge)
Wednesday, July 17th, 2019 AT 2:17 PM