As you can see after I couldn't get the water or lava to load on brake I used the default minecraft way and it says block filled but it does not, so something is blocking the block for really been placed even when using fill, the command is been triggered right but sadly it's just not working something is braking the spawning of the water or lava
I think this one was fixed in this ticket: https://mcreator.net/tracker/issue/45568
This bug will be fixed in 1.8.2. Thank you for your bug report!