I have 3 views in a "Page" stack view with proportional heights ("Title" 0.07, "Contents" 0.88, and "Controls" 0.05). Page is constrained to the safe area and everything works fine until I add another stack view within the Contents view. I get conflicts on all three of the height constraints previously mentioned, and four automatic constraints come up in conflicts. I am guessing the problem comes from the lower two views in the stack, because they get an automatic constraint with a +1 at the end. But that means they are adding a pixel to my views whose heights are proportional to the Page stack view.
Autolayout working in one VC but not another
Turns out it was just a bug. I copied the main view and pasted it, and deleted it again. The constraint errors disappeared on their own. As I worked through this app, the same issue came up a number of times and I fixed it this way