Earlier quoted context omitted.
Once upon a time I had a problem with remote control. It woukd stop working from different positions, but from time to time, not always. It took a while for me to realize there’s a heating radiator behind my back in that directions. And it went hotter or colder depending on thermostate. I guess at one point its IR output would overwhelm IR output from remote control.
When I first read this comment I was picturing a hot water radiator behind you, so it sounded unlikely based on the blackbody radiation curve for ~320 K. But now I realize you're probably talking about an electric heater. Given that their heating elements get so hot that they're putting out visible red/orange light, it seems very plausible that an electric heater could produce enough ~940 nm IR to drown out the signa…
Btw. that Nokia 6310i from 2002/3 is still used today by mother-in-law, and original battery still holds for 4-5 days!