ford f-350 transfer case?

[Rybo]

Me n my bro were driving to work in a company truck the other day and the transfer case broke. Our mechanic claims it broke cause we had the hubs locked in. And our foreman says he never heard of such a thing cause he drives around with the hubs locked in all the time so he doesnt have to get out and lock them in if he needs 4 wheel drive and he has the exact same truck with around 10,000 less miles. So whos right? I think the truck is a 04, f350 with a utility body. About 100,000 miles