Observer doesn't detect several block state changes

The bug

Observers do not activate when the following changes happen:

• A campfire becomes a signal fire (hay block placed below)
• Adding an eye of ender to a portal frame
• Powering a door/trapdoor that's already open
• Fire catching on another face of a block
• Vines spreading to another face of a block
• Fences/panes/walls/iron bars changing connections
• Stairs changing shape
• Grass becoming snowy
• Adding/removing a music disc from a jukebox
• Adding/removing a book from a lectern
• Leaves distance changing (log placed nearby)
• Locking a repeater
• Note block changing instrument (block below changed)
• Note block getting powered
• Tripwire changing shape/connections
• Snow layers generating from snowfall

Related issues

• Hoppers getting powered: MCPE-40843
• Pumpkin/melon stems moving: MCPE-36783
• Nether wart growing: MCPE-41074
• Note blocks changing note: MCPE-53919
• Entering a bed: MCPE-46345
• Rail changing direction: MCPE-30544
• Respawn anchor charged: MCPE-75742
• Target block getting hit: MCPE-84391
• Kelp age changing: MCPE-179683
• Various fixed issues: MCPE-14710