Download stops for some reason

When i try to download more than one video, one or two videos are downloaded then download is stopped by app. I tried downloading max. 6 videos but i only downloaded 2 or 3. Still connected to a wifi but download does not continue for some reason. I had to delete queued videos from the list of my talks, then i found the videos by searching their name and download them one by one. This is so overwhelming.

Aslihan5674 about TED, v2.5.2