yeh same, as my comment below. its either 1. when internet drops, the connection gets momentarily severed between you and the server, resulting in that the permission expires as it thinks you are trying to DL it via a new session. or 2. servers permissions expire after a certain time, if your DL is not fast enough the expiration gets triggered.
I hope DEV has an alternative DL source like MEGA or Dropbox on their patreon.