As shown in the attached video, chests, piston arms, and some block entities will fail to render partially, or completely upon entering spectator until the player gets close to the blocks.

Steps to reproduce:
1.) create a world with the spectator mode enabled,

2.) in creative/survival, place down some pistons, chests, or other block entities,

3.) move 15-20 blocks away from the placed blocks in any direction,

4.) change into spectator mode,

upon switching, some of the block entities fail to render properly until the player nears the blocks, or changes back into creative/survival