Can't copy/paste in Word Online

I've been using Word Online for the past 2 weeks, and I keep facing a problem. Sometimes it work, sometimes it doesn't. I copy a few lines to paste it somewhere else in my text and it works, but then when I try to copy another line, it won't work ; Even if I use cut, it will cut the text, but when I paste it, it keep pasting the first lines I copied. As if it doesn't want to copy the new lines I am tryingt to copy. It just won't work, but it only happen in Word Online.