/fill does not send all block updates. GIF demonstration from Kris Madas.
Command block Bug !!!
/fill command does not always send block updates
Structure Blocks in load mode don't load when activated by a redstone source placed via /setblock or /fill
/fill-ed redstone blocks will only power one command block at a time
Concrete powder doesn't fall.
/fill redstone_block is full bugged
No redstone updates after using the /fill replace command.
/setblock does not update the placed block consistently
Lamps, Signs Fence Gates, and sheep eating grass don't give block updates!
/fill only supports block entity tags for one of the filled blocks
Block particles displayed in corner of area when using destroy option in fill command