Thanks for your post, @Jasper6. That sounds pretty unexpected.
I was able to replicate what you are seeing by doing the following:
Selected a text layer in Figma Design.
Made sure it was set to the thinnest font weight.
With my mouse positioned over the canvas rather than submenu, I scrolled down.
Interesting to note that this did not happen when I repeated these steps with font size. Anyway, I’m going to file a report with our team. Thanks for reporting this!