Purchase a Bosch laser level - ~45$ USD- this will make putting up anything shelf/picture etc a breeze. And get a label maker and properly label your circuit breakers- it will make your life much easier when you have to deal with wiring issues/swapping out fixtures-

The case / buttons alway throw off the reading- just get a cheap torpedo level-

Side note. Natural slate comes with a lot of maintenance. Frequent sealing and it will flake and chip. It can also have very uneven edges leading to misaligned joints.

If this is your first time tiling- do a small bathroom w some inexpensive tile first. Practice on a less critical room.

counter sink the holes a bit also - the screw will have pulled the edge of the hole out a bit and this will cause the repair to sit proud of the surface- Same trick works for drywall holes-

check the connections of the wires for the sensors at the motor unit. The thin wire can crack and short out/disconnect as the motor operates. - one quick question- when it stops and reverses, does the light flash?