Can't walk down L-shaped stairs with 2-tile desk underneath

Well, you're onto something @Bluebellflora .

I'm getting this:

Dining table, empty: Works

Dining table, with chair in middle, no computer: Works

Dining table, with chair on side, no computer: Works

Dining table, with chair and computer in middle: Does not work

Dining table, with chair and computer on side: Does not work

Dining table, no chair, computer in middle: Works

Dining table, no chair, computer on side: Does not work

Desk, empty: Works

Desk, with chair on side, no computer: Works

Desk, with chair and computer: Does not work

Dining table, no chair, with computer: Works