Why am I breaking Pitlock spring washers so frequently?
I reached out to Pitlock DE about this question specifically (I'm an authorized North American retailer since 2006) and heard this back:


  Regarding the question of your customer about the spring washers, I
  talked to our technicians. The spring washers are wearing parts in
  theory but they shouldn’t break that easily. If you press the key
  firmly into the lock when opening and closing it, the washer should
  really last a long time. We’re in close contact with a lot of
  customers here and seeing their and our own bikes, the washers have
  lasted years with fairly regular mounting and unmounting. The thing
  really is to press the washer down with the key when opening the lock.
  Of course, there can always be an issue with the washer itself. 


So while this is a part that is expected to wear over time, the experience you (and the respondents in this post) are seeing is unexpected.

We do offer replacement spring washers on our site, here: https://www.urbanbiketech.com/collections/accessories/products/replacement-lockring

If anyone else is having an issue with unexpectedly high failure rate, please feel free to reach out to me directly (via our contact us page), and I can help rectify the situation with the manufacturer and/or provide an appropriate discount on replacement products.