Hi OzChris,
A quick web search on that firmware version leads me to believe that you have a BYO Draytek modem. I am not sure which model you have, it might be worthwhile to make sure you have the latest firmware version.
Are you downloading files from the same location on all of these devices or are you downloading from various locations? Can you advise what type of files you are trying to download and how large they are?
- Shelly