Yoyogames' latest GMS 2.3.7 is breaking the text_typer because it adds a true bool type.
Fortunately, It's very easy to fix.

Go to text_typer User Event 2
At lines:
Line 126 command shadow
Line 132 command outline
Line 196 command instant
Line 202 command skippable
Line 412 command gui
Line 559 command skip_space

Change is_real to is_bool

This concludes the fix.

Note: Using those commands, you must use true or false to make the command work, e.g., {instant true} and {instant false} will work, but {instant 1} or {instant 0} wont work.