Unlike paintings, boats, item frames and glow item frames, armor stands cannot be placed in the same block as scaffolding. This is inconsistent with other block-like entities.
[media]
MC-224418
Inconsistency: Cannot place armor stands inside of scaffolding
Open
6
(Unassigned)
Confirmed
Gameplay
Low
Block states, Entities
armor_stand
1.16.5, 21w17a, 21w18a, 1.17, 1.17.1, ..., 1.19.4, 23w18a, 1.20.1, 23w33a, 1.20.4
Retrieved
Can confirm. If you first place the armor stand and then the scaffolding, it works.