Door lock fault in hot weather

Hi folks. The heat is upsetting the rear( I think ) door lock sensor. No trouble till the last couple of days. Alarm both key and remote sound the horn briefly indicating a door fault. Dash indicator shows a door open and rear window won't operate. usually slamming the rear door does the job but today no go. Rear of the car facing the sun and very hot! As soon as the temperature drops the problem goes away. How do the door sensors work? Are they adjustble or do I need new parts? Any help appreciated. 2004 HSE 5 door TD4.

Thanks, Terry.

Moved the car into the shade 1/2 hour ago, all working fine, back to normal??

Terry.

Oh dear, am I the first to suffer this problem?