My Viper gets stuck in the spin cycle quite regularly. This has happened pretty much ever since I bough it.
I find that if I take it apart there is a piston that moves horizontally to change the flow of water from forward to spin. When it is stuck in the spin mode I see that the piston no longer moves. If I removed the end cap attached to the valve that causes the spin cycle, then lube that end of the piston it will work for another month or so. I'm using some lube from the pool store, but am wondering if there is something better? I would not mind doing this once a season or so, but monthly is crazy.
The lube is called Lube Tube with PTFE.