Don't loading file (throws error) with using Camunda External Task (JavaScript)

Hello there. I’m now trying to load file or it’s content to manipulate with, but facing issue on loading file on
await file.load() step.

I just simply starting process with variable named “file” with file type and file itself named text.txt with content - test , and I’m trying to get file’s content in external task by using file.load().

Getting that error

SyntaxError: Unexpected token e in JSON at position 1

Attaching screenshot