After digging some mineral underneath some sand my Dupes started digging sand as it was falling and kept going until I stopped the dig command on that tile.
The graphic for falling sand is stuck in a loop
So far seems harmless and doesn't heavily impede gameplay but I did not see this bug in the tracker unless I missed it. You can't see it here but the tile underneath the falling graphic of sand is also registering as a infinite dig tile just with no graphic.
I was on the highest speed setting and used the click and drag dig command for the area. I clicked the tiles underneath the sand first then click and dragged the sand right after. Otherwise I do not know what caused this.