https://imgur.com/a/7DNF9mrPlease help us help you and fill where relevant:
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Hello! In an "Array dual scale" question, I'm looking to equalize the width of the columns of answer choices in the table. From my understanding they should divide evenly, but as you can see, the "Jamais" column is smaller for some reason. Do you have any idea how I can fix this?

Printscreen :  imgur.com/a/7DNF9mr

There seems to be something wrong

There is no column to separate the scales but the jamais-column seems to replace it.
You should send this question as lss export
Copy the survey, remove all but this question, send this as lss

Hi Joffm, thank you for taking the time to answer me.

Here's the requested files, I hope this is what you were asking for. After trying some things, I found out it may (or may not?) be related to the "Mandatory" option in the "General options" of the question. When I activate it, it does equalize the width of the columns, but the problem is 1. I do not want that column in my scale; 2. Since its taking more place in the table, its causing the rest of the answer choices go out of bound (see the attached image). 

 

And you didn't change anything in your theme?

It must be a theme problem, this is what I see using the vanilla theme.