I am not aware of any systemic problems, never heard of a single failure of these switches. I don’t know how to respond to “I’ve heard” stories. Who/what/when? ... if you want to contact me offline. This part was approved as part of the TT22/TN70 STC. Obviously any part can fail, and pneumatic connection can leak And the installer should do whatever test they usually would when touching a aircraft pneumatic system. This actual series of World Magnetic switches are the same ones I used for year in scientific equipment applications, frequently abused and never failed.