When the screen turns black, don't panic, wait for 30 or something seconds, and then tap "back". It's like the video hasn't been loaded, but the pack is awarded anyway. Works for me.
By the way, the availability of videos depend on where you live. I've encountered no problems in South America; and the situation with them is generally better than it was in Russia. There I got 5-10 videos per day (sometimes 0 despite trying all day). Here I always have the full amount.