Re: Trying to determine the cause...
Bite splints can be higher on one side to artificially level out the cant. Also they can be 'indexed', made with cusps and grooves so you will be closing into a fixed position to centre the way your lower jaw functions.
I am wearing upper and lower ALF appliances to widen my arches and will soon go into Damons for the final phase. I had earlier extraction orthodontics and ended up with multiple issues caused by what they call a 'distally trapped mandible', my lower jaw was forced to close too far back because my upper jaw had been retracted. Symptoms were multiple; killer headaches, breathing problems, dizzyness, neck pain on on it went. I had absolutley no idea the effect of extraction retraction orthodontics would have. Treatment now is walking me back to class 1 occlusion and getting the extracted premolars replaced either with implants of bridges. My posture has improved so much I stand taller no more forward head posture which I think was causing all the tension in my neck and shoulder - the head is heavy and needs to be centred over the spine to properly distribute it's weight. There is some interaction between lower jaw position and this balancing I can't quite explain it but there are studies showing the link.
Symptoms were mainly left sided which I was told is for some reason the most common.