error when generating snp files from a variable

Hello everyone, 
I have a testbench for generating s2p files from a SP simulation that was working until few months ago. Today I have reopened (w/o making changes that I am aware of) and I get the error as shown below:

first I show the testbench settings:

notice how the s2p generation is disabled: the field "file" is left blank

in the corner I defined some parameters, "filename" is the word that is suppose to generate the name for the s2p. 

where the two variables are defined as follows

And now the output log:

spectre.out file gives the following error:


When clicking on the error message at "9", the input.scs file opens up and the line 9 gets highlighted in green



now, so far I understood that the problem seem to be related tom the "pathcds" variable, but I really don't understand what the error message here means, since I don't see any error in the input.scs file

by the way - if for instance I define the variable "filename" as shown below, then I get no errors:

thanks
Tommaso