Started making fuel line with Evil Energy PTFE hose and fittings. As I get to the last threads of tightening the fitting the hose begins to turn with the fitting nut. What am I doing wrong? I seated the ferrule and could see the liner fully in the ferrule. Hose slid right on the fitting and no part of the outer SS or nylon was caught in the ferrule. Should it be lubed on the hose before assembly? I lube the threads with a drop of light oil.
I did finish one short line from the cell to the filter and pressure tested it with air submerging the fitting in a bucket of water and there's no leaks.

When it's fully tightened and assembled correctly, there will be a small gap between the nut and the fitting. That's normal. I do use a bit of lube on the fitting threads, but when it's tight it's tight. The nut won't always go all the way to the fitting.

Look closely at the fittings and you'll see what I mean. I run the same stuff.

https://imgur.com/a/e7iq5Tr

I was under the impression the nut had to tight all of the way against the fitting.

I also never get them tightened all the way together. Never had an issue at all.