While placing multiple blocks or stacking them takes a bit to load block grapics starts as a black outlined invisible cube then develops graphics takes a couple seconds
not a big deal doesnt really bother me just something wierd I noticed
Likely you were somewhere near an area with a huge amount of block-lights (eg rukios lighthouse). The black outline invisible cube shows that the blocks have in fact been placed, and we’re simply waiting for the meshing to complete on the second thread.