Dave, you are 100% correct - issues with the fuel tanks, plumbing or debris in system is normally the problem. However all is can say in that one weird specific problem I had, gluing the cap on the nalgene UAT solved my issues. May have been some small defect on bottle threads, who knows. Prior to that one experience I had used nalgene UAT's on other jet with no issues. I only offered my cap gluing as a suggestion to Mike as something to try.