the starlight liquid does not stop flowing after the source block is broken. (I have a waterfall that won't go away after an accidental spill) Also the starlight dust and crystal needed to from a crystal cluster disappear from the starlight liquid without forming a cluster. (considdering this is the only mechanic to reliably farm stardust at this is a real problem as you need 1 to make it and only get 2 out)
May have been a visual glitch. I have had client glitches like that where I remove a source block and the water stays until a server reset unless I place and pick up the liquid a few times until it properly updates.
seemed to have been some sort of glitch. A few days after this post the problem stopped, although I had the problem for several days, so I presume it must have been some sort of update that fixed it.