I made a Minecraft map in 1.15.2 where opening a trapdoor would trigger an observer and start a chain of commands. I made a command block to replace the block where the observer was with a new observer to reset the system. In 1.15.2 (I don't know if it affected 1.16) the observer wouldn't get triggered when it was placed with a command block. Now, every time I replace the observer with a new one, it triggers the chain of commands.