According to Nintendo's Error Code Lookup, the 108-0075 error code may indicate a possible "bandwidth" issue, but your Internet speed should be more than fast enough to handle this download, so I'd more suspect there might be some type of "wireless interference" from another electronic device, or possibly a "DNS" problem.
So try checking out the above url (or copy&pasted below) for more information, but if still no luck, perhaps you might want to give a call to Nintendo's 1-800-255-3700 (6 am ~ 7 pm Pacific, everyday) Customer Service number, and one of the service representatives can do some over the phone troubleshooting to determine exactly what the problem(s) might be, and then talk you through any needed steps to correct this.
Situation:
- The update stopped and the error message "Unable to connect to server was received."
- May occur if a system update, game update, or Nintendo eShop download timed out.
What to do:
- Try the update again.
After starting the update again, the download will continue where it left off. [How to]
- Check your network's available bandwidth.
If other devices or programs are using available bandwidth, or if your Internet connection has slowed, your connection with our services may time out. [How to]
- Check for wireless interference.
Wireless interference between your Wii U and wireless router may be causing the download to time-out.
As an easy solution, try moving the Wii U into the same room as your wireless router during the update, and then moving the Wii U back once the update is complete.
If you are unable to do this, try our more extensive wireless interference troubleshooting. [How to]
- Enter an alternate DNS into your Wii U console's settings.
Using an alternate DNS may improve your ability to complete the Wii U system update. [How to]
Still Not Resolved:
- If the issue persists, please contact us at 1-800-255-3700. Specially trained representatives will be available to assist you, 6:00am - 7:00pm (PST), seven days a week.