The bossbar for the raids get funky if you die while a raid is ongoing.

The bossbar doesn't show: 2 mobs left or 1 mob left ect...

Each time you spawn in a new pack of illagers to do a raid with the potion effect then the bar fills up a little and when you then kill them it goes down. But it never goes down to 0 and gets removed. 

1 minute video showing and explaining the bug