PS - WBSE Substitution not working properly

Hi gurus

I have a created a substitution with following steps:

Step 001

Prerequisite: none

Substitutions:

Field UF unit 1 WBS is substituted by Field PRPS-POSID

Step 002

Prerequisite: PRPS-USR00 LIKE '*:*'

Substitutions:

Field AA element is substituted by constant value X

The problem is with Step 001: the field is being copied without the special characters of the PRPS-POSID so in Step 002 PRPS-USR00 never contains ‘*:*’

Any ideas on how can we copy special characters as well?

Thanks in advance!

Rgds, C.-