Call a finite collection of tiles that can tile the plane if we have to use each tile at least once tiling.
Is there a collection of at least 3 tiles that is not tiling, but such that after removing any one tile from it we get a tiling collection?
For example, a set of two non-compatible, tiling singleton tiles is such a collection.
I intentionally didn't define what I mean by tile because I'm interested in all sorts of constructions - it can be Wang tiles or your favorite geometric connected or disconnected polygonal or (simply) connected region with translations or rotations.
It is easy to see that on a line we cannot have such a collection of at least 3 Wang tiles.