[Observium] Cisco 3750 Temperature

Here's an odd one...

Temperature is reported correctly by many models of Cisco catalyst devices but on one of the Observium nodes there are two 3750 switches with different behaviour. The 3750 with IOS 15 is okay and reports temperature but an older 3750 under IOS 12 doesn't return temperature, even though I feel sure that it did a few years ago.

Observium version: 18.5.9244 (24th May 2018)

Has anyone else observed this behaviour?

Update: Just checked an old 2960, still on IOS 12 and found that it doesn't display temperature but a 2960 with IOS 15 is okay.

Any advice gratefully received.

Thanks

Darren