Supposedly the water block is flowing, but the actual result is not flowing.
How to reproduce:
Crouch on top of the command block.
Place the water bucket. The popup for the command block should open and that results in this glitched block.
Linked issues
duplicates 1
Attachments
Comments 2
This issue is being tracked at MCPE-178348.
In my case, the command block is in Needs Redstone, so don't expect Always On setting to be turned on