Are you using a VPN?
Have you tried logging out and back into the minecraft launcher?
The water on the left and right is not flowing straight. You are picking up the source blocks, but they get reformed when 2 blocks of water have 1 block of space inbetween them. I don't think this is a bug.
[media]Middle water block got picked up, but got reformed due to intended water mechanics.
Reproduce:
Setup Command block to spawn cows:
[media]Spawn Cows:
[media]Kill Cows:
[media]SOME Items can't be picked up:
[media]++ Confirmed in 18w30b
You should be able to change mousewheel sensitivity in the options.txt file in the minecraft folder.