Placing Eidolon's Wooden Altars crashes the game on dedicated servers. The same behavior can be replicated using Straw Effigies. In Singleplayer, the blocks do not get placed, unless questing has progressed far enough, which I assume is intended behavior.
Log: https://paste.ee/p/O1Q8j

The same behavior occurs without actually placing them. Interacting with a chest while holding them is enough