[Richard L]

I think I know what may have caused this fluctuation.

The HFS-3 flow meter and FAV is mapped to accommodate up to 3x 1mm jet. When you are running only one 0.8mm jet + 0.5mm restrictor, the flow signal is amplified, as seen on the SC setting. Becuase of this the resolution/smoothness of the flow signal is decreased.

I can reflash in another flow sensor map for you so that you can get full resolution. For this to happen, you need to return the controller board back to us, service is free. Before making this decision, are you going to continue to run this system at such a low flow in the future?

Try increase the failsafe delay trimmer (clockwise), this may solve your failasfe problem due to over shoot of the flow signal.