Knock sound from rear left top (video) any suggestions

[neo_rambo]

Hey guys I have had this weird knock for a couple of years and I can't figure it out. I have checked the suspension, sway bar ends, the inside of the cabin where the drive belt assembly is. I just can figure out where it's coming from the sound seems like it's inside. Any suggestions on what the check? The only thing I haven't checked is to take the left cover on the rear wheel to check to see what's under that. https://www.dropbox.com/s/otkymbrniu...14429.mp4?dl=0