Massive caster variance Side to side
Strut rod tuning is needed at times to dial in the caster sweep.
I have done hundreds of alignments with a tape measure and a caster/camber gauge (Longacre). We used to take them to the alignment rack and have them double checked to a while. The numbers were always good so we started skipping that step.
One thing that helps with consistency is to make a 3/4"-16 adapter for the gauge. I prefer this to the magnet for both repeatability and consistency measuring side to side.
Adjustable strut rods and tubular UCA's make the alignment process much easier.
Lastly, I have had cars that went through multiple ditches, etc. that aligned quickly with even measurements side to side. On the other hand I have aligned very nice unrestored cars that fought me for a few hours trying to get things in spec and even side to side. As said each car is it's own mission of discovery.