I saw some other instances of this bug by searching but thought I could help by narrowing it down some. The bug is where the canvas isn't visible after zooming past a certain level. For me it seems to only happen when a canvas dimension is a power of 2.
Example on a 1024 x 1024 canvas stuff disappears at 16x and closer.
But 1024 x 1023 works AS WELL AS 1024 x 1025 (both all the way to 128x).
I tested it at other dimensions and it seems to be governed by the largest dimension that's a power of 2, and happens in a very predictable fashion, with for example canvas size 1024 x 2048 having stuff disappear at 8x and closer.
Great tool, I'm really liking it as I'm getting the hang of it!