Why does installing Shadow of Mordor from DVD take so incredibly long?

While I'm computer savvy, I know nothing about modern gaming systems. We bought our son a pre-owned Xbox 1 for Christmas, along with a pre-owned game of Shadow of Mordor (and other games).

He tried installing Shadow of Mordor, and it was taking a very long time, until it got to 86% and just hung. It stayed at 86% for about half an hour before he gave up, rebooted and started trying to install it again. This time it (eventually) got to 81% before hanging.

Is this normal behavior for Xbox 1 games and is patience the only solution, or is this a sign that something is wrong with either the Xbox 1 or the game, or is there something else possibly wrong? (I don't think it should matter, but we have a reasonably fast fiber-optic connection to the Internet.)

Edit to add: After trying it a third time, he tried disconnecting from the Internet based on advice he found elsewhere (again, this is from a DVD, not from the internet), but that didn't help and possibly hurt. This time, when he got to 81% he just waited it out. A half hour later (now) and it's at 82%. So, it's apparently not stopped installation, it's just going very slowly.

Edit next day to add: While leaving it overnight to finish installing, it had still not finished when I woke up. However, by the time my son woke up a second time (he'd woken up earlier to see if it had finished), it did indeed finish installing — taking more than 12 hours to install!