How to reproduce
Place a fence
Use an armor stand on the top of it
Expected result
Same as using spawn egg on fence:
[media]
MCPE-79487
Placing an armor stand on a fence or wall causes it to fall through
Open
9
(Unassigned)
358264
Confirmed
Multiple
1.19.10.20 Preview, 1.17.20.20 Beta, 1.16.0.63 Beta, 1.14.60 Hotfix, 1.16.100, ..., 1.18.31, 1.20.40.22 Preview, 1.20.30, 1.20.81 Hotfix, 1.21.60.28 Preview
Retrieved
You can get the armor stand to rest on top of the fence by placing it one block higher and letting it fall. You can also get the mob to fall down by using the egg on the side of a block next to the space above the fence. The only inconsistency I can find is when you point exactly at the rendered top of the fence.