Once the settlement increases a bit in size, my citizens keep getting stuck. There is no obvious reason why they get stuck - Ive checked for physical obstacles and such.

Has anyone come across this and found an efficient way to deal with it?

There is a message something like "Got stuck while going to xy". They can't reach the entrance of this building. Building this in a new spot with more place at the entrance worked fine for me.

That might work, thanks for the tip!

The last game I played, about 1 in 4 new immigrants got stuck in a tree at the entrance point, all periodically spamming that they can't reach the village center. I assume they wouldn't unlock their phones for border officials.

Lots of villagers get stuck in their own houses while those are still in the stage of building - there's no way to get them building their houses differently. And while all those people are stuck, noone is doing the work. The moral of my villagers has dropped into minus ...

I had 333+ villagers in my game and the problem was in every case not where they were but where they wanted to go to. And this was never a house but always a building set by myself.

If they can't go to their own house, maybe you put something in front of their entrance? Did you delete their house and they built it again in this position?

It was obviously one of those bugs. I saved the game, logged in later again - and everything was fine ...