Steps to reproduce
High in the sky, make a short row of blocks with a chest at one end. At the opposite end place a copper chest on top of the last block, and spawn a copper golem on it.
[media]Place a stack of items in the copper chest.
After a while, stand on the wooden chest and run /setblock ~ ~-16 ~ glass
Expected result
After step (2), the copper golem places items into the wooden chest.
Observed result
The copper golem places items into the wooden chest only after step (3).
I have found that farmers have the same dependency on finding a solid block below farmland before they can interact with crops. The distance to the solid block is determined by the mob’s follow_range. Villagers have a follow_range of 128, so farmer will harvest and plant as long as there is a supporting block within dy = 128 below the farmland. Copper golems have a default follow_range of 16.
That might make this issue WAI, but on the other hand it might be reasonable to give copper golems a larger follow range so that they will not be restricted in floating builds.