If you are falling over your heels on this trick it actually may be from over rotating. By the nature of the rotation of the backroll to blind thats done late (as opposed to mexi), over rotating means landing with your hips further away from the down wake than your shoulders causing you to try and salvage the trick by cutting back toward that down wake, or in most cases just falling over your heels. This is comparable to, lets just say, a toe side back roll... which people learning it for the first time often over rotate the trick because of the mentality that they think they will catch their toe edge if they don't rotate fast enough. Both the ts br and the hs br to blind have a toe side landing and thus to stick either requires less rotation than tricks that have a toeside landing that rotate in from the other direction (ex; frontroll or crow mobe). Sorry this post ive typed is getting pretty technical i hope this isnt too difficult to follow.
Check out this video of some of my early backroll to blind's (link below). I too do them with a more late style and in the video you can clearly see that there is some slight over rotation forcing me to cut back left (my left, riding) toward the down wake to salvage.
I don't consider this trick incredibly difficult to land, but it definitely takes a lot of practice to ride away from consistently. Overall its a pretty boss trick and its super cool that you're doing it... I would suggest that you try and film what your doing because that always makes things a lot easier!