GMC 2008 Yukon Denali Owner's Manual page 44

Q:
What is wrong with this?
A:
The belt is twisted across the body.
1-40
CAUTION:
{
You can be seriously injured by a twisted belt.
In a crash, you would not have the full width of
the belt to spread impact forces. If a belt is
twisted, make it straight so it can work
properly, or ask your dealer/retailer to fix it.