Back in 2006 or 2007 I think there was a failure like this reported on TBN. But I haven't seen one since. I think that fellow thought the cam gear was getting too much side load from the hydraulic pump...but I am stretching a poor memory. They have since updated the cam with a shrink fit cam gear instead of a bolt-on gear, which is of course stronger. It is only sold as a cam/gear assembly. The cam is also extended and is now supported additionally by the front cover. It is just a more robust design.
If this is a defect, that is exactly what a warranty is for, defects in material or workmanship...but the kicker is that even if you can prove a defect and absolutely no neglect on your part, reimbursement is still limited to problems that manifest themselves in the time period (time or hours, limits on both). If you have a 2007, you had a three year warranty, so you are out by maybe 2 years. Just giving you a heads-up on how that normally works, so you do not think the fact that this has been upgraded is a smoking gun leading to coverage.
The good news is that the new design is super stout, and if you can do the repairs yourself it should not be all that expensive and you won't have to give that cam gear another thought.
Talk to your selling dealer and see how he can help. I just looked it up and the kit is part number 006004516F91 and is not as expensive as you might think since it looks like it comes with the cam/gear, cover, gaskets, bearings, compatble hydraulic pump gear, etc. Looks complete. We have sold quite a few 7520's and we have not seen one fail, so it isn't common. We have never installed the kit ourselves.
I hope this helps, and good luck getting this going. Sorry this has happened to you, but at least the fix is an improvement.