In creative I used lava buckets on the side of a single row floating stones. Creating a (one block strong) wall of lava.
That makes one source block next in mid air to another!
After placing another block where the lava source block is (which means I have deleted the source block) the lava drops only about 1 block and the lava wall still stays there.
Even when I delete the next lava row.
Changing to survival doesn't update it.