Remco Scheffer

Confirmed this issue for 1.16.1
We can see normally with Blindness under water.
We can however, not sprint with the effect on, as is normal with blindness, so the effect only fails to work visually.

I've been experiencing this issue too in a 1.14.4 singleplayer map. It seems to happen for me on redstone repeater / comparator clocks whenever the chunks have been unloaded. It happened twice when I died and went back later on. The clocks has stopped working and if a repeater were placed in those same coordinates they would still be unresponsive.

I have confirmed this issue, or a very similar one still exists in 1.14.4.
I believe it happens to Passengers. When an entity is riding another entity that can walk around.
In this case when these entities stand on chunk borders, are unloaded by the player moving too far away, and then loaded again when the player approaches.

My steps to reproduce this were,
1 Creating a 1.14.4 single player world.
2 Moving out of the spawn chunks to chunks that will unload.
3 using the following command while standing right on a chunk border: 
   'summon chicken ~0 ~0 ~0 {Passengers:[{id:armor_stand}]}'
   in order to summon 5 chickens with armor stands on top of them.

4 teleporting far away before they moved around to let the chunks unload.
5 teleporting to a closeby location and then walking back to the place where i summoned the chickens.

I tested this 4 times and in each case there were several missing armorstands afterwards.
For every armor stand that disappeared I got the following kind of messages in my log:

[18:54:09] [Server thread/WARN]: Wrong location! (64, 21) should be (63, 21), atl['Armour Stand'/36450, l='bug fixing', x=1024.09, y=70.45, z=347.43]
[18:54:09] [Server thread/WARN]: Wrong location! (63, 21) should be (64, 21), atl['Armour Stand'/36455, l='bug fixing', x=1023.91, y=70.45, z=346.25]
[18:54:09] [Server thread/WARN]: Wrong location! (63, 21) should be (64, 21), atl['Armour Stand'/36459, l='bug fixing', x=1023.94, y=70.45, z=341.31]
[18:54:09] [Client thread/WARN]: Received passengers for unknown entity
[18:54:09] [Client thread/WARN]: Received passengers for unknown entity
[18:54:09] [Client thread/WARN]: Received passengers for unknown entity
[18:54:09] [Client thread/WARN]: Received passengers for unknown entity
[18:54:09] [Client thread/WARN]: Received passengers for unknown entity
[18:54:10] [Server thread/WARN]: Fetching packet for removed entity atl['Armour Stand'/36459, l='bug fixing', x=1023.94, y=70.45, z=341.31]
[18:54:10] [Server thread/WARN]: Fetching packet for removed entity atl['Armour Stand'/36455, l='bug fixing', x=1023.91, y=70.45, z=346.25]
[18:54:10] [Client thread/WARN]: Received passengers for unknown entity
[18:54:10] [Server thread/WARN]: Fetching packet for removed entity atl['Armour Stand'/36450, l='bug fixing', x=1024.09, y=70.45, z=347.43]

I attempted this with a few other entities but so far I could only make it happen with armorstands, interestingly, this issue didn't occur when the chicken had NoAI:1, so perhaps it has something to do with the entity moving around?