AP9631 temperature sensor stuck

[Anonymous user]

Hi everybody.
Today found my 3 smart UPSes showing constant temperature on their temperature sensor 1.
I tried to fry sensors with my heat gun, no reaction. Tried to change port, tried to change sensor - no reaction. No errors in apc logs.
The only thing worked for me was to reboot their management cards, after restart i can see true temperature in their web console.
How is it possible to have all 3 stucked!!!???
Their configurations:
1. Smart-UPS RT 3000 XL, Firmware revision 5.1, AP9631 HwRev 05, sumx v6.2.0, aos v.6.2.0, bootmon v.1.0.8
2. Smart-UPS RT 3000 XL, Firmware revision 5.1, AP9631 HwRev 05, sumx v6.2.0, aos v.6.2.0, bootmon v.1.0.8
3. Smart-UPS RT 2000 XL, Firmware revision 416.8.I, AP9631 HwRev 05, sumx v6.2.0, aos v.6.2.0, bootmon v.1.0.8

This is a serious problem, because we using this to monitor temperature in server rooms.
How to prevent this?