Started about a month ago? I'll get to 75% or 90% or so, and then the download just stops complete. No pausing or restarting seems to fix it. I've been wondering if it's something to do with Adblock Plus or other protective software.
I don't really use Mega anymore, but I did use it the other day and that was happening to me too. I eventually gave up after a few attempts and just used the megasync app and it downloaded without problem.
Sounds like it might get around any sort of antivirus or adblocker complication that I suspect is what's preventing Mega from consistently completing downloads.