77 degrees is typically considered ideal water temp for the RO membranes, higher and you can technically produce more RO per gallon, but going to far will prematurely age your filters, and going way above typically 110+ will start melting the film within the RO membrane. When your temperature is lower you will produce less RO per gallon but your filters will last longer.Good information. My RODI does an automatic flush but not long enough to get to cool water. I will try running a faucet in the same line prior to starting to fill the ATO reservoir. Appreciate the advise.
Sorry, OP, but I cannot think of anything else that you have not tried. Perhaps try ordering the membrane from another supplier? Is there a chance that the ones they sell you are just old? Also consider getting your water tested independently.
Most of the ratings for RO membranes are based on a water temp of 76-78 degrees (F).