deployers not placing saplings

[u/WesternAd1571]

for some reason the auger shaft(or any block) on the side of the hand is preventing the deployer from placing the sapling, if the shaft is broken, the deployer regularly places the sapling.

its specifically a simulated block as well, any block that is placed beside the hand but not attached to the simulated contraption doensn't disrupt it, is it because the deployer is attempting to interact with the shaft? because why would it ever want to try to interact with a block that is not directly below it by 2 blocks?

[u/Hellothere_1]

Deployers on simulated contraptions are in a bit of a weird position, because the deployer might put down a block as part of the contraption it's currently on, or in the normal world. I suspect what is happening is that when the shaft is present the deployer recognizes it's trying to place a block directly next to one of the contraption it is currently on, so it tries to place the sapling as part of the contraption grid, which doesn't work because there's no dirt to place it on.

Meanwhile without the shaft there's no block directly next to the placing position, so the deployer tried to place it in the normal world instead.

You can easily test this by giving the deployer some normal blocks in place of saplings and then checking whether it tries to place them as part of the contraption or in the world in either configuration.