I’ve documented the circuit in a thread on my S70 that I’ll link to shortly. This is quite aRube GOLDBERG system so brace yourself before you look at the diagram

Both the interior lights and locks are controlled by 2/76 lock controller logic module

The problems you are encountering might point to failing door lock actuators. If they have never been replaced, they are due. When they start failing, it's always only on hot days. There is information on this on this site, you will have to search for that. But I would try and diagnose in this direc...

Each door lock motor has a small protection device. As designed, if the motor should draw too much current and begin to overheat ( for instance, because of a stuck switch ), the device opens the circuit to the motor to keep it from melting down or damaging switch or relays contacts in the system. As...