Definitely my favorite game of the whole game jam! :)
I was able to hit the enemies the enemies through the walls and they could do it too and it was easy to trick the AI near the border of the walls and the enemies were also stacking in a corner even though there was no entrance and I was just behind the wall separating them from me. Kiting was also very effective against them.
Aside from that the gameplay is awesome! I definitely think you can expand on it and make a something more serious.
Ohhh that's exactly the same problem I had on my own project (on Godot though) for this game jam so I totally get it!
The moment a collision is modified on a navmesh that is set in stone everything goes wrong! ^^ You'll need some custom logic then. One way to enhance it a little bit is to make the enemies slide in the narrow entrances with path finding is to use sphere collision shapes.
For kiting a simple solution (until there is a better one fitting your game) would be to make then run a little faster than the player so that you can go back to them while they enter the retreat state.
