I had a leaking issue years ago. My dealer asked 2 questions, how full was I filling it and how tight was I turning the cap? I was filling them to within about 1/8-1/4" of the top and turning the cap as tight as I could by hand. I was told to only fill them to just below the bottom of the threads and to only tighten the caps moderately tight. I changed both and the leak issues stopped. I did both at the same time so I don't know if just one of those would have solved the problem. I was told also that if I re-tighten the caps after the initial tightening that was likely breaking the seal that had been made. Try those, it may help, however mine were not the gallone bottles.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.