@Yannick_Duguay thanks so much for updating your post! I hopped in and opened the Read-Only link of your site in Safari as it was a flexbox Safari based issue.
You had your “wrap- testi page testi 25” class with a flex child flex basis setting of 25%.
Changing that style to “Flex Expand” for the mobile landscape viewport resolves the issue as you can see here:
Please let me know if this solves the problem, if not, I’m happy to help further 