iPhone 6s (iOS 9.3.2) won't download video when on battery (and battery at/less than 66%)

I seemed to have run into an odd glitch that I'm trying to figure out if its part of iOS 9.3.2, part of the iPhone 6s or part of the video-owner's/app's problem.

Also: Please, no judgment on my video watching choices 🙂

I was using the Dramafever app to download video episodes. After successfully downloading several episodes, the next episode would not start to download.

I began troubleshooting many possibilities: (wi-fi was working, wi-fi data not capped, wi-fi signal strong, I was able to otherwise read email and use the internet on the iPhone, just NOT able to download ANY episode from the dramafever app.) I also did things like: close and restart the app, and also click the power button as if to turn the iPhone off, but instead hitting cancel, in an attempt to clear any cache on the phone.)

During this time, my iPhone 6s, with 9.3.2 loaded, was NOT plugged in and was running on battery. The battery reading read 66%, the last I looked at it.

Then I plugged my phone into the charger, while the screen with the 'stuck' video (that would not begin to download,) was on, and the video IMMEDIATELY began to download.

I then ran my battery down, and at 70% it was downloading videos from the Dramafever app smoothly. At 68% when a new video was to be downloaded - the app and iPhone again refused to start it. While watching the screen, I plugged the device into a charger, and wham, it immediately began downloading.

FYI: the video size is about 640MB, HD video.

I will attempt to replicate this with Amazon Prime downloadable videos, HOWEVER --

HAS ANYONE HERE EXPERIENCED ANYTHING LIKE THIS?

Does 9.3.2 or 9.0 stop downloads when on battery? It seems like it could at a much lower battery level, but 66% is so high, I am surprised if this is on the iPhone end. I'm suspicious that it's on the app's end.

I'd like to know so that I can discuss this with Dramafever and let them know that this glitch or potential problem exists-- if its JUST their app.

But 9.3.2 hasn't exactly been the smoothest update to 9.0, so just wondering if this is a problem across other apps or if anyone else had an issue like this with another app or service.

Thank you!!