The bug

When using the new /place feature command, I noticed that the command was returning an error message even thought, some part of the feature has been placed.

It only worked with this command in the water:

/place feature minecraft:clay_pool_with_dripleaves

As we see on the two following screen shot taken before and after the execution of the command, some clay has been placed on the coasts.
Also, the bug doesn't occur every time (It's pretty rare).