Hi,
i know there are tons of posts about this subject but I'd just like to offer my experience.
My car was a total engine out and apart stripped body even wiring harness out basket case when i got it luckily for free. . . .
Anyway I'm down to doing the brakes on the car.Master is shot so i get new one,it had the steel washers in it under the grommets.Fluid resevoir was cracked so found a new one.So there were also the remnants of some sort of hard plastic lines crumbling and deteriorated that went from reservoir to master cyl.So those are NLA as far as I could tell
but I did find at one vender short 90 degree steel feeder tubes that press into grommets
on master C.Then i get a length of brake fluid rated rubber hose,red actually not blue from another vendor and at this point figure i should be good to go.
Wrong.
seat feeder tubes,bleed master,bleed brakes.awesome!
Until morning puddle of brake fluid on floor.
Pull master check everything.Appears to be bad sealing point where feeder tubes are seating on the nifty little washers in the master.Weird.
re-install very carefully and i noticed because there was some fluid in my bench bled MC and that the slight
side load or actually pulling up on the feeder tubes is breaking the seal from feeder to steel washer
this seal was already starting to weep fluid The MC isn't even in position yet.
I've decided to make my own feeder tubes that I'm going to bend slightly so they follow the firewall through the pass through hole without the weird 90 degree bend that is causing the leak.
Once my new feeders are through the firewall I'll continue with red flexible brake fluid line to the the reservoir.
I'll post if it works

Just going through this myself as I managed to finally break one of the original nylon MC feed lines. Lasting 50 years my "soft lines were pretty robust. You should have had a 6 inch length of steel tubing connecting the nylon feed line to the MC, circled in green.



The flare on the end of these lines is what sits on the washers in the MC.

The fluid seal in the MC in port
is from the grommets, not the tube flare on the washer. The washer is in there to keep the tube flare from sitting flush with the floor of the MC and not allowing fluid to pass through ports which are "drilled" more horizontal than vertical in the MC. If your losing fluid out of the feed openings it is likely the grommets not fully seating. It can be a PITA to get the grommet shoulder seals seated but you'll hear a nice metal on metal click when you do. (the flare seated hard against the washers)