The bug
Multiple actionbar-area messages can coexist. When a new message appears, it overlaps with previous messages instead of replacing the old one.
How to reproduce
1. Run the command /title @a actionbar command message
repeatedly
2. Play a music disc in a jukebox
3. Start riding a pig
4. Observe the actionbar
Expected behavior
All messages are aligned to the same height, and any new message clears any old one.
Confirmed in 1.16.20 and 1.16.100.52 beta. Please fix this overlap !!! thanks
Can also be reproduced by scrolling over enchanted items. The enchantments will overlap with the HUD / hotbar