I have the same problem. Even though I'm well aware of it, even though I take great pains to make sure my easel is level, even though I use a ruler and measure -- still my buildings etc. come out tilted.this thing about the distorted subject always happens to me when I try to draw from life, especially played, small figurines,
which I usually place on my left next to the paper, as in the photo of the Troll.
I don't know why I tilt them so much, even knowing it it always happens to me, noticed when I had tried to draw more from life.