https://us.forums.blizzard.com/en/wow/t/vicious-saddle-bug/829300/4
A blizz staff said it’s a visual bug. Hopefully that’s true, because after being stuck at 30% for about 2 weeks, I dropped back down to 0. Meanwhile a GM told me it was stuck because I had gained as much progress as I could for that week 
didn’t think there was a limit.