King

Armor too 

Its not a desync, its just that the Xp orb texture and entity arent actually connected, the texture is its own particle, you can see this in action by running "execute @e[type=xp_orb] ~~~ particle minecraft:balloon_gas_particle ~~~"

You actually can add multiple target selector, BUT it will not auto fill for you with tab, you have to manually type it

still works, just doesn't fill for you

You Crouch with the shield in hand to activate it on bedrock edition.

The /particle command works perfectly fine, Heres a list of all the things you can send with it.

This behavior is caused by the texture of the xp orb, and the xp orb entity being totally disconnected, the xp orb will stay behind as the texture follows the player, making it seem like you can't pick it up. heres a video demonstrating this, the xp orb entity location can be seen with the particle command but the texture of the orb can move independently. https://cdn.discordapp.com/attachments/305834249913892864/639722524216918029/Minecraft_2019-11-01_03-07-50.mp4

I am also having this issue. It works perfect for a couple hours and then stops working.
I can move my mouse fine in the UI.
In the game I can click and use the scroll wheel fine but mouse movement isn't captured. I tried changing sensitivity but that didn't do anything.

I first noticed when I was playing on a modded version of MC at version 1.12.2, It would work fine for a couple hours and then stop working and would never work again unless I completely rebooted my computer. I then downloaded the official loader from Mojang and started a 1.14 world and it still did not work.

I tried mouse and touchpad neither worked

Mac OS Catalina 10.15

is was the snapshot