It sounds like your deadzone setting is too low and the controller has some stick droop issues. Increase the deadzone size until the movement stops.

Its defiently not the controller, I tested playing with the keyboard without the controller plugged in and it didnt help. I followed a tutorial to fix the stick droop and that still didnt help anything. Then I tried adjusting the deadzone. First i followed your pdf tutorial on how to adjust deadzone and it got worse, then I increased it a very large amount and that made it very much worse. I am may be adjusting the deadzone wrong? I thought I tried about everything with the deadzone but I could be wrong

What you need to make sure you do is move them to the center and then start moving them horizontally until your player starts moving do the same with the diagonal ones and see if there is any changes

Do you have second controller you can use for testing in place of the current controller? This is almost always caused by one of two things: either a controller with drooping sticks and needs deadzone adjustment (which you can test by replacing with another controller), or in rare cases it is caused by PC memory issues when a PC is connected and your are playing in Simulation Mode or Play Mode. In the case of PC connection what normally happens is the player keeps moving the same direction after you release the direction key. Please confirm which issue you are seeing.