Ludovic B. Matt J. I noticed this as well, has been going on for a month for me, since I started using Relume.
I will say, I just opened Relume in Safari which I don’t usually do and 1) some of the buttons are missing styling on the wireframe builder page, you can’t see what they are, but 2) the dragging and dropping for some reason is WAY better on my Mac M2 in Safari, than it is in Chrome. Like Ludo, the chrome experience was pretty buggy/slow and things would get frozen in place, dropped in the wrong spot, page becoming unresponsive, etc. In Safari these issues are non-existent, so there might be some clues to fixing it right there. Not sure why that would be the case, but it’s what I noticed🤷🏻♂️