If you have multiple tabs open and drag the final one to re-order, the right-hand side of that tab doesn't have the correct rounding:
Once it swaps place with the other tab, pay attention to the original tab being dragged, it has a similar same error to this (now fixed):
https://orionfeedback.org/d/5018-rounded-first-tab-ui-glitch-if-next-to-a-pinned-tab