Bosses bug with ZeusTrap Marksman

hello all!

look at my video and compare his life (and dmg that im doing) from 0:15 to 0:17 then 0:17 to the rest of the video… it looks like im doing NOTHING. Unfortunately i cant explain what’s wrong, it happens with most of bosses on all monoliths, if you see the video you’ll understand that comparation.

i’ve uploaded on my google drive, link its below (please tell me if i need to upload in another host):

thanks!