Right now there's a known issue with the PS4 version where if you don't turn your system off properly you are forced to re-download over 22gb worth of data. I'm in the process of re-downloading the game right now for the 6th or 7th time and am very frustrated.

Anyway, I expect your issue relates to this. If you aren't doing this already-- try and make sure you're logging out through the main menu proper, then closing application instead of just turning your system off or putting it into rest mode while you're playing the game. I had my system go into rest mode and had to re-download once.

Rest of the time, for me anyway, its been power outages since where I live in Florida storms almost daily during the summer.