[Richard L]

This is interesting, the failsafe window is wide enough to cope.

Try two things:
1. increase the "FLSF SENS" trimmer by advancing it a few degress "clockwise". I gathered the naming of this trimmer is quite mis-leading. Clockwire to slow down the repsonse time. (range 0.2-0.7 seconds)

2. Unplug the tank level sensor so that it doesn't cause visual confusion to the fialsafe trip.

The amount of liquid you are injection is relately small compared to what the system is capable of. By inceasing the sensitiveity of the system with SC trimmer, you will be loosing some sampling resolutions. It causes more "over-shoot" and "under-shoot" of the flow senssing circuitry. By incrasing the "FLSF SEN" (clockwise), you are averaging the incoming signal so minimising the false trigger of the failsafe threshold.