Creating a .txt file with multiple echoed lines of text fails depending on the text

I'm a casual coder trying to make a bat file that writes a txt file with multiple lines of text and it's not working for some reason. My code so far for reference:

@echo off

(
  Echo;extends "res://Mod Data.gd"
  Echo;
  Echo;func_init():
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
) > "Output\custom.txt"
pause

(It might be unnecessary to put all the test stuff here but I put it there just incase that's what's causing it.)

When I try to run it, it closes instantly and doesn't work, but if I try to run it without "func_init():" it works like a charm.

Also, I made another bat file testing this out by only printing "func_init():" and that worked just fine as well, so I have no clue what this could be.

Batch isn't smart enough to know that the ) in Echo;func_init(): isn't the end of the code block, so right now your script is aborting because it thinks the : is a syntax error. You can get around this by using the ^ character to escape the close parenthesis.

@echo off

(
  Echo;extends "res://Mod Data.gd"
  Echo;
  Echo;func_init(^):
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
  Echo;test
) >"Output\custom.txt"
pause