I was also thinking about bad normals. But the jitter happens even against a big flat vertical wall, far away from its vertices. But maybe, my surface was double-sided?
Thanks a lot for teaching me the word “welding”. I was thinking about merging the vertice of the adjacent walls of my dungeon, now I know what to google!
To be fair, I ditched the physics out of my code for now; I don’t need it yet, there are other things I must write first. I let Panda manage my collisions with its Pusher and that’s very much okay at this stage. However, be sure that I’ll come back to you guys when I’ll put some physics again, you’re good 
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Oh, and btw, PhysX license is weird indeed :/.