When a Comparator is reading the contents of some blocks through another solid block, the Comparator will not update its redstone signal if the block it’s reading from is removed, until either the comparator receives a block update or a new container that can be read by a Comparator is placed. This bug affects the following blocks:
Bee Nests & Bee Hives
Cakes
Cauldrons
Command Blocks
Composters
End Portal Frames
Lecterns containing a Written Book or Book & Quill
Respawn Anchors
To Reproduce:
Place one of the aforementioned blocks in the world. Place a solid block of any kind adjacent to that block, then place a Comparator facing outwards from that solid block.
If the Comparator is not powered by default (for example, with the Cauldron or Respawn Anchor), configure it so that the Comparator is powered.
Break the block providing the Comparator with power and observe how the Comparator does not update.
Provided is an video demonstration using a Respawn Anchor as an example.
This is already being tracked in MC-120986 and MC-94566 (I have inquired internally about the possibility of consolidating these two reports).