At the risk of this looking like a nercopost...
I just recently had some things go haywire with a my Systema TW5, after scouring the depths of the internets, I was having difficulty finding the replacement parts, in this case, the FCU. In a last ditch effort I decided to reach out to Z-shot. As most will know Z-shot is the American distributor for several brands including Ares, they also used to be the distributor for Systema, though if you look on their current website you won't find any mention of Systema anymore. Anyways, I contacted them by email and received a response in a couple business days. After a few messages inquiring about the item model number and a description of the problem, they issued an RMA and have agreed to take a look, much to my surprise. I'm about to send my TW5 off to Ohio, I hope all goes smoothly. I will post updates as the situation develops.
Anyways, if you are still looking for repairs for your PTW, you may want to reach out to Z-shot. After all, for what it costs to get into a Systema, they should give you the royal treatment (in my opinion).