Tunnel under the crystal
It is possible to start a tunnel under the crystal. But the earth close to the crystal cannot be removed, so the bricktrons are stuck endlessly digging the same voxel.
This is an issue I forgot to post about as well.
If you create a landscape task, they will attempt to remove that top layer of dirt from under the crystal, but cannot, due to those blocks being indestructible. This causes them to be stuck attempting to do it forever, as nothing is telling them that they cannot do it.
The solution is to either allow them to remove the top surface layer, or a better solution is to make it so it is unpathable, and thus, not a valid goal in the task. (Similar to how if the area is clean, a cleaning task has "No goals").
Thanks! I've forwarded this to our QA.
Thanks for the report and it is fixed for the next update!
Thanks for your supports!