Changing text formatting behaves weirdly

Hello, I'm having a weird issue with changing the font withing the text.

I am making rolling credits. I copied and pasted text from an Open Office document, cleaned up the formatting, and am now putting some of the text in italics.

But on some lines, but not all of them, if I change one word, it changes the text that comes after on the right.

(see on the photo attached : first line is okay, second isn't, the name on the right shouldn't be in italics)

It does the same things with any change I try to apply to the text (colour, font, size...)

The problem appeared when I started on this project a few days ago. I let if off or the week-end, come back today, it works fine ; then suddenly the weird issue comes up again, but as I said, only on some lines. I can't see any difference that would explain. I quit Motion, restarted the computer, to no avail.

If anyone as ideas...

I am on Motion 5.6.3, Monterey 12.6