Hi @egomm
I was able to reproduce the behaviour you are seeing in FME 2018.1 builds. The error occurs attempting to select a template sheet via the file browser button.
As a workaround, please type in the template sheet name instead of selecting interactively via the dialog window. Alternatively, FME 2018.0 builds (18284-18312) appear to not be affected.
I have filed a PR for this issue and will be following up in this thread when it has been resolved. My apologies for any inconvenience caused.
Hi @egomm
The issue has now been fixed in the latest release of FME 2018.1 (build 18567). You can download the latest FME release here.
Thank you for helping make FME better!