Hey Don
Let me ask you just a few question:
1. Did you replace the 60 year old brass fittings or did you clean and inspect them for cracks?
2. Did you use stock brake lines? No Stainless Steel, Al., Cuni or Nicu lines?
Some fittings have different angles for seating to different material tubes?
Are you using slotted box wrenches for a tight fit, makes a difference.
Someone asked me why I went through my rebuild and didn't use Stainless Steel.
My answer was 'The old steel brakes lines lasted 60 years,
I'm 50 (in a few days) and don't think I will out last my new steel brake lines I put on'.
Hope this helps, but others may have a better solution?
Terry