Bizarre change in aspect ratio

I started Mobile Suit Zeta Gundam yesterday and it was in its original boxed aspect ratio like any anime before the 2000s would be and yet as I sit down to watch it today the aspect ratios all of a sudden full screen, which it’s clearly not meant to be, even the other episodes I watched that were not full screen aspect ratio now magically are and I have no idea how to change it back, has anyone else run into this sort of issue?