I'm another one who thinks a lot of this problem will miraculously go away when using a 6 or 6.5" ruler, spread out your fingers across a wide area.
One of my sayings is that "fabric can be treacherous". It does want to do all sorts of things on its own and can be difficult to be kept to the straight and narrow
Even though I am big on prepping my fabric first and doing all sorts of things, I do check/straighten my fabric every 2-3 cuts just to make sure everything is still where/how I want it.