So I'm doing changing my timing belt, and with the new one on with a new tensioner, when I turn the crankshaft clockwise by hand the belt starts walking off the crank and cam gears.  I put the old belt back on with the new tensioner and it stays where it should.  It's a Rock timing belt, P/N TB500, that I purchased from a well known vendor.  Could the belt have issues?  Has anybody seen this before?

Thanks, Josh.

Years ago, I put on a new altenator, water pump, power steering pump and the darn thing would roll over.
Never had this issue before.
Did the same as you, put old belt back on and no problems.
Gathered a different new belt and problem went away.
If it's not working, put on another new one.
If problem is cured, the belt supplier should go good on the malfactured one.
L

There is likely not anything wrong with the belt.  If you are turning the engine over (or running it) with the crank pulley off, then that is why the belt is walking off.  The crank pulley keeps the belt from walking off the front of the lower timing belt gear.