I added another 1 1/4 pipe as an overflow tank, that can catch the ink that exceeds the volume of the timer if something prevents the timer filling action from stopping so that the ink will not leak out of the ink pressure regulator in case of a fault.

With this pipe and the sensor in the vacuum line, the machine should be prepared for all sorts of faults that can be caused by stuck sensors.

Other faults may occur like failing check valves or relays, but I guess preparing the machine for such faults would be too much, especially because they may never occur at all.