I am getting a very intermittent P0116 (General CTS fault)

I have replaced the CTS on the gounds that it was cheap, easy and quite likely to be the issue. All was fine for a month but now I am getting it again.

Of course it is a "Schrodinger's Fault" so wont misbehave while I am looking

However, I do note that the thermostat seems to be opening early. Might the ECU be programmed to flag a failure to reach operating temperature within a reasonable time as a CTS fault?

Or am I clutching at straws??