Constant ” Download unsuccessful.” notifications

I’m constantly harassed by these “<Untitled> Download unsuccessful.” notifications.

After taking the above screenshot, I cleared the entire notifications list. Within the next three minutes (usually even less), the list was already overflowing again.

I’ve learned to manage the symptom by navigating to the Download Manager application settings; hitting FORCE STOP, followed by CLEAR DATA, and CLEAR CACHE. Although the notifications slowly start showing up again. Just one at first, but gradually increasing in number with each occurance. Within a day or two, the numbers are usually back out of control.

I have no idea what it’s supposedly attempting to download, or why. But whatever it is, it’s not instigated by myself. I could just disable download notifications, but I’d rather identify the underlying problem and kill it directly. Needless to say, I’m not too keen on my devices automatically trying to download random mystery files from the internet. Any ideas? Thanks.

FYI: The device in question is a ZTE Blade L5 smartphone.