Automator variables show as $(D682B6F8-7C03-4C8A-92A6-9118EE827DE1) instead of entered text

I often have to batch-rename files at work so I'm writing an Automator Application to help me. For example, I'll often need to add R1 to the end of the filename to show that this bunch of files are revision 1.

Here's my Application in Automator. Sorry I couldn't find another way to display this on these forums other than this giant image:

My problem is, instead of adding the text entered, that's stored in the variable named "suffix", the script adds a long string that appears to be hexadecimal. It looks like some kind of encoded variable ID. Here's an example:

$(D682B6F8-7C03-4C8A-92A6-9118EE827DE1)

So if drop "filename.pdf" on the icon, and enter R1 in the get text dialog, the file will be renamed filename$(D682B6F8-7C03-4C8A-92A6-9118EE827DE1).pdf instead of filenameR1.pdf.

I tried adding a "Show notification" action in the middle of the script to show me what's in the suffix variable and it works just fine in there - the notification will pop up with R1 (or whatever I type in the dialog. but the same variable in the Rename files action gives me the long ID string instead.

TLDR: Does anyone know how to access the contents of the variable in the rename finder items Automator action?