The issue was exactly as we mentioned; the containing flex had grow/shrink: 1. I noticed lots of other issues as well where grow/shrink are set to 1 which ends up suishing components if they don't fit, % units are a bit average I would recommend changing to rem, including for font sizes, also adding gap: 0.3rem or similar to your flex containers, in particular the flex repeater.
.
However, I would suggest that you want the bottom row of buttons to always be visible, so in that case you would need to wrap all of the components above the bottom button row into a column flex set to grow/shrink:1