ADUM1410 and ADUM1412 problem


We are having a big problem of reliability components  ADUM
1410 ADUM1412 we use in a system under railway.
Here are the typical electrical interface we use components.
As you can see from the diagram the nominal 24VDC supply is removed from  the
vehicle with the power inputs properly protected.
The problem is evident only when we install our equipment on the vehicle in  a
particularly disturbed. 
In the laboratory it has never shown any problem, also the device has  passed
all the necessary tests to EN 50155 certification.
The problem we are encountering is the following. 
Randomly and without a logical explanation some components undergo  alterations
of their characteristics, but there were no malfunctions, 
if the operating temperature is below the 40/45 ° C. 
As this temperature is exceeded the component stops working because the  input
of the 5V power supply is short-circuited.
In this condition, the power supply enters the protection and de- energises
the component. 
After about 1 second the feeder attempts to return power to the component  but,
this remaining in short circuit back into the power supply protection.  
This behavior, with a duty cycle of 1 sec. continues until the temperature
drops below the threshold of 40/45 ° C.
Can you give us an explanation for this strange behavior of ADUM Thank you  

Best regards
M. Menichini

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