Originally Posted by DragonSnooz
Now notice the UI when shooting an arrow from low ground
Smallest of Low Ground
Now look at the attack roll in the combat log grin Disadvantage was not applied.
The Combat Log

If you don't have percentage to-hits that are even multiples of 5, you have Advantage or Disadvantage. Those images clearly show that you are at disadvantage from low ground (56% isn't an even multiple of 5) and the combat log is what is messed up (it isn't showing the disadvantage).