Stammering Parasitic Z-wave Events/Commands ?!

THE FACTS
One week ago, and using the Events trace within the IDE, I started to observe a very peculiar behavior for my 13 Z-wave battery-operated Temperature sensors (over 12 v1-Hubs and 3 Locations) :
Starting 2015-12-18 6:48 PM CET, and ending 2015-12-18 9:16 PM CET, I observed HUNDREDS of identical Temperature reports, one every minute for every Temperature sensor, when normally I get one every 4 hours.
Apparently the problem started randomly at about the same time for all 13 sensors, and ended spontaneously 2 hours later for them all.
Then yesterday, I discovered an even more bothersome problem : all my battery-operated Temperature sensors would wakeUp EVERY MINUTE, when they are actually programmed to wake-up every hour.
You can imagine the disastrous impact on battery life…

THE PROBLEM
Since all those Temperature sensors are connected to different Hubs, in different Locations, and have been bought at different times, more than 6 months apart, I cannot imagine those problems to be a hardware issue related to the sensors themselves.
The most likely suspects (first common intersection in the Command chain) are the Hubs or the SmartThings cloud.
They have been known in the past to “forget” Events or Commands, so why not send them multiple times now…

But the last problem is even more worrying : the Temperature sensor handler is hard coded to set (once) the wakeUpInterval of every Device to exactly 1 HOUR.
For ALL those Devices to wake up every MINUTE, “somebody” would have to send a different Command, with 1 MINUTE instead of 1 hour : who ? how ??

And as you can imagine, I did NOTHING before the problem appeared, no new Device insertion, no Device Handler update, no nothing.
AFAIK, the exact same configuration worked for more than 6 months without exhibiting those problems (or I missed it).

SOME BACKGROUND
The Hubs are all v1 US, Firmware Version 000.013.00013.
Z-wave Temperature sensors are Fibaro FGK-101 (US version).
A custom Device Handler (that I developed) controls them : “JJ’s Fibaro FGK-101 Handler”.
It sets (normally once and once only) the wakeUpInterval to exactly 1 hour using Command :
"…zwave.wakeUpV1.wakeUpIntervalSet(seconds:60*60, nodeid:zwaveHubNodeId).format()…".

As you can imagine, once ST support (request #171339) read “non-ST Z-wave Device” and “Custom Device Handler”, they discarded the problem as not their own.
But I cannot imagine anything, except one more SmartThing instability, which could explain my symptoms.
What is VERY worrisome is that the stammering wakeUps every minute could occur only with some spurious wakeUpIntervalSet Command “spontaneously” generated and sent by the Hub to my battery-operated Devices.
Hard to believe, even after suffering for months of multiple ST platform bugs and instabilities : up to now, some SmartApp would be disabled, some Events/Commands would be lost, but none would be “auto-generated”, thus destroying previously set Z-wave Devices parameters.

But outside of Gremlins/hackers or an unnoticed EMP pulse, I cannot at that time imagine any culprit other than the ST platform (Hub or Cloud).
Any idea ?