Sorry, I deleted the world that this originally happened on. I haven't seen it since then though.
Based on my own testing, the light level of the water in the water logged block doesn't change based on the environment and is always at 15.
[media][media]This is the expected result I believe. When you have a repeat command block the default is no delay after it's activated, hence execute on first tick is on. You can turn in off if you want to add delay when the command block activates.
Even if it's not technically a bug it should still probably be changed so that the scroll bar pushes out to the right instead of pushing to the left and reorganizing the inventory.