Lava in lakes in the nether is not properly updated

Lava in lava lakes in the nether is not properly updated.

1. Create new world in creative mode
2. Create a nether portal and go to the nether
3. Find a nether lake that should flow down

I tried this 3 times. First 2 times with superflat. Last time with normal world generation. No other settings and in all 3 cases I was able to find the same issue.