This is a known issue but unfortunatley I haven't quite figured out what causes it just yet. Unity's text UI works as it should but in certain resolutions it simply breaks apart. As soon as I found a fix, I will update immediately! :)
Have you tried TextMeshPro?
Not yet but it's definitely on my todo list. I kinda rushed the demo a bit last montgh so I rather used what I already knew instead of learning the better thing on the spot. Well and now I have a weird bug so yea :D But yea TextMeshPro is probably the way to get rid of this bug.