I have a city that is permanently stuck at mutinous, despite being 100% stability for many many turns. Cannot build anything besides stability districts and infrastructure. Increasing the stability has no effect.

I believe it may be a bug in the game state that led to my ownership of the territory. I went to war with AI Green, AI Purple was also at war with AI Green. I took over the city and it was considered "occupied" giving it very low stability. A few turns later AI Purple vassalizes AI Green, and I lose control of the city, ie. it's given back to the vassalized player. This gave me a grievance, which I exercised, demanding the city back. AI Purple, then gifts the vassalized city that I had conquered back to me. After this, the city is permanently in mutinous for over 50 turns, despite spamming stability districts and having 100% sphere of influence.

Also have this bug. 

Was at war with AI Brown, won the war and took city. Now city has 100% stab (always did) but won't let me build as its 'mutinous'. Interestingly I took two cities, and this only affects one of them. The one that it is happening to was originally owned by another AI, and taken by AI Brown. 

J

I too have this issue. The Red AI attacked me, cause I’m the only one with a different Religion period, so every nation is Angry at me about it. Red AI took one of my Cities, I took it back plus another 2 and as it is my first game didn’t quite get all the areas I wanted, but I have a better idea now. It was 100% stable before it was taken and has been at 100% since I got it back, just continually says it is Mutinous. My only thought is to absorb it into another City, but it is already quite a large area, so I would need to detach a couple of Outposts first, make one of them another city perhaps, to educe the cost and still have access to a city. I was also able to purchase Machu Picchu despite there not being one tile marked as a Mountain on the map, at all, so I bought a Wonder I can’t use… At least I’m learning a lot during my first game.

same problem its a huge bummer because its my capital.