Some events / actions do not trigger observers

The bug

Observer blocks do not detect the following actions:

• Chests opening/closing
• Ender chests opening/closing
• Lighting a nether portal
• When a command block is successful (can be detected with a comparator)
• Beacon activating/deactivating
• Something teleported by the end gateway
• Ringing a bell by hand or by projectile
• Brewing stands finish brewing a potion
• Ender dragon head being powered/unpowered
• Left clicking a note block (might be intended)

Fixed

• Fixed in an unknown version (presumably in a 1.17 snapshot):

• Grass blocks changing into podzol blocks when a 2x2 spruce tree grows

• Fixed in 20w14a:

• Don't react to the state change of fences/walls/bars/panes when a tree grows next to them

• Fixed in 1.14.2:

• Shulker Boxes opening/closing
• Don't react to the state change of fences/walls/bars/panes when large mushrooms grow next to them

• Fixed in 17w47a:

• Playing a note block
• Adding or removing a plant from a flower pot
• Farmland going through intermediate stages of hydration 0–6, which appear dry
• Locking / unlocking a redstone repeater
• Connecting / Orientation (north, south, etc) State for Cobblestone Walls
• Shape State for Stairs
• Changes to the data value of fire that signifies flammable surfaces surrounding fire
• The change of facing fences, (stained) glass panes, iron bars, pumpkin/melon stems, tripwire and redstone wire
• Snowy State for:
• Grass Block
• Podzol
• Mycelium
• The opening/closing of the top part of a door by hand, as opposed to by redstone power.

• Fixed in 16w44a:

• Grass/ferns growing into tall grass/tall ferns
• Grass blocks changing to dirt due to sheep "eating" the grass
• Anvil damage changes
• Dragon egg teleports to a destination
• Inserting or removing music discs from a jukebox- ¹
• Dry sponge becomes wet
• Changes in number of snow layers
• Placing/breaking top part of a double plant (MC-31038)
• Chorus flower growth to chorus plant
• Opening and closing door, trapdoor or fence gate
• Vine/Crop growing (e.g. cocoa, potatoes, nether wart)
• Placing/removing bottles/potions in/from brewing stands ¹
• Placing an eye of ender in an end portal block ¹
• Changing the water level of a cauldron with a glass bottle or water bucket ¹
• Switching comparators between comparison and subtraction modes.
• Sleeping in beds.
• Changing command block/structure block type
• Changing command block to conditional/unconditional
• Repeater/comparator/detector rail/activator rail/powered rail getting (un)powered
• Nether portals be lit/activated
• End portals be activated