Xenoxsis

So I made this robot. And I want it to grab lava from an EnderIO tank. Job done.

Below the robot is an infinity water source (3 water sources in a row, robot hovers over center water block) - I mean to make obsidian. I try to have the bot equip a bucket and fill with lava from internal tank, that works. Now finally, I try to use the bucket in order to place the lava from the bucket. No dice.

I tried with, and without water. I tried placeDown(), useDown(), swingDown() etc etc. - I get a true "item_placed" from the bot, but nothing is happening in the world, and the bucket is still full.

The bot has an inventory upgrade, inventory controller upgrade, tank upgrade and tank controller upgrade. And I tested with a solid block, worked fine with both placeDown() and useDown(). But not with the lava or water bucket. I even threw in an Angel Upgrade (though my logic suggests that I shouldn't have to).

Can anybody identify what I am doing wrong?

Sky factory 3 v. 3.0.15
Open Computers MC 1.10.2 v. 1.6.2.7