I got some stretchy edges…
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It’s the way you map the texture. flat, cube, cylinder.
Also, the default cube has its own UV-Map, if you made them round, then the UV-map isn’t aligned anymore. Not sure where you are on the course, but maybe the next lessons will clear things up.
Have you re-unwrapped the cube after making those soft bevelled edges?
Have you checked for UV stretching with the “Display Stretch” option in the overlay settings? Everything looks fine to me, but maybe it could help.