Rob
Ansys Employee

Re the journal, /read/case-data stuff is a safer form as the / symbols mean the command is executed as a block. The first / also means it must be executed from root level. If any part of your journal has an error returned it's going to go very badly wrong. 

Re the output, as you've not told the code anything about HOST and NODE it'll execute on all compute nodes. There's a section in the UDF manual that ought to help resolve the problem. NaN, nan etc is "Not a Number" so usually means a value is infinity or nonsense in a report, but the solver is able to continue. It can also mean the reported number won't fit into the format you've told it to.