cancelling build order does not cancel dig

Interesting bug but I can't reproduce it and I thought i knew what might be going on. Phantom dig orders left over from build orders could have been a thing, but i've tried several times and can't get the hats to stick. This was a bug at one point a few updates ago. so maybe it's come back under unusual circumstances, but for me, they don't even bother trying to dig those tiles. Even when they get the promotion, the orders get cleared when i cancel the build order. either by clicking the blueprint/ghost, or via painting over it with cancel all, or cancel buildings - no digging is done.

The only oddity I discovered was that material deliveries have to be made prior to digging. And that canceling a build on an embedded build order causes the delivered materials to become lodged in the natural/preexisting materials after you cancel the build. The material returns to the pool of available materials, so it's sweepable even when buried.