The bug
If multiple bossbars are active, the notch opacity of the second bossbar and below is messed up.
Linked issues
is cloned by
is duplicated by
Attachments
Comments
This bug still active in 1.15. I just upgraded my server from 1.14.4 to 1.15 and the bug was there.
migrated
Can confirm. I was setting up notched boss bars to make a meme but the one below it was messing up so I used a progressive boss bar instead. I don't have a screenshot of the notched versions, but mine behaved exactly how yours did.