If you run the old job (from 1995) you should obtain the same solution in Version 5.20 (except for known Code changes). You said "steam header", so I presume this is a 31.1 run? Maybe pressure stiffening of the elbows is causing the problem - try turning that off in the Configuration and see if that is the difference.

If you can't get 5.20 to give you the same solution as 3.20, send us the 3.20 files (_a and _j) as well as the expected output, so we can take a look at it.