BGE/UPGBE expression controller stops to work

Scripts are executed by python controllers. They are controllers and need to be triggered by at least one sensor to execute. They do not trigger other controllers.

Btw. this belongs to all type of controllers.

To trigger a controller you need to setup a sufficient configuration on the sensors. In your case you could have a property sensor that checks if property frame equals 1070.

Alternative you use a property sensor that checks if property “frame” changed and you check the value within your controller.

I suggest to read Prof. Monster's BGE Guide to the GameLoop. It explains in detail how the logic is executed.

In addition to that, I suggest to read Prof. Monster’s BGE Guide to the Python coding. It might help you to dive deeper into the BGE.

CU