I found this in the current Lix 0.10.23, but this bug must have been in the physics forever, at least since I've presented C++ Lix in 2009 to the Lemmings Forums.
Expected: When you assign blocker to a miner, the lix starts blocking.
Observed: Timed well, on the right terrain, the blocker assignment cancels the miner and makes the lix walk again.
This cancelling works with a batter assignment (instead of a blocker assignment), too.
Explanation: The floor must be shaped like a builder bridge. In the physics, the builder bricks are 2 hi-res pixels high, i.e., 2 units of distance. Naively, this is too high a drop for the miner to continue, therefore the miner has leeway in its code to continue mining along such a bridge. To trigger the bug, assign blocker while the miner is hovering over an air pixel, i.e., while the miner's foot is at Foot1 or Foot3 here:
Foot0
+--+--+--+--+--+--+--+--+--+--+--+--+
Foot1| | | | | | | | | | | | |
+--+--+--+--+--+--+--+--+--+--+--+--+
Foot2 | | | | | | | | | | | | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
Foot3| | | | | | | | | | | | |
+--+--+--+--+--+--+--+--+--+--+--+--+
Foot4 | | | | | | | | | | | | |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | | | | | | | |
+--+--+--+--+--+--+--+--+--+--+--+--+
| | | | | | | | | | | | |
+--+--+--+--+--+--+--+--+--+--+--+--+
Bug! Bug! Bug!
-- Simon
