However I have "collected" now 15 of the failed units (more are coming with a little help from my friends) and the failure appears to be within the internal bussing that is encapsulated in a sealed "potting" epoxy (a royal PITA to dissect let me tell you) of the reed switch.
IMO there is either an internal cold solder issue or mechanical vibrations and possibly temperature fluctuations are instigating the failures. The real problem is the issue often manifest intermittently. So when the tech checks the circuit using a DVOM or GDS2 may appears OK. These almost always result in a "comeback" for repeat failures.
But I have "close acquaintances" that have had a new sensor fail in 3-6 months TWICE! (which essentially instigated my desire to solve this issue once and for all, as in many cases it was I that turned them into Volt fans)