The robot continues to mow, even though there is heavy rain.

The following is the robot's behavior when rain is detected:

Islands On:

The moment rain is detected by the robot, it will wait about 1 minute to make sure it is not a false detection. If the rain detection still exists after 1 minute, the robot will stop the blades and start searching for a corner on the lawn. This is because if Island is installed on the lawn, the robot will not acquire the first wire it reaches, since it can be an island, which will cause the robot to spin around the island. As a result of this behavior, it may take the robot longer to arrive back to the Base Station.

Islands Off:

Q1.

Q3. Raise the Rain Sensor sensitivity by going into Mower Options --> Rain Sensor --> Sensitivity, and increasing the value by one segment to observe if this was enough to make the change on the robot. The higher the Sensitivity setting is, the more sensitive the robot will be to detect rain.
Raise the Rain Sensor sensitivity until you find your desired setting.