It looks like they saw the uxexchange.com link (which is now broken) and tried to fix it by replacing uxexchange with ux.stackexchange.com. I honestly would have thought that would work too, but apparently it didn't; the post ID must be different.
If you can find the post you meant to link to, just switch the link over to find that post.
Not sure if these links were ever redirecting right, but the uxexchange.com domain is returning a 503 service unavailable message right now. Stack Exchange doesn't own it, so it might just be down for good or something.
This is "fixed" per Let's fix these UX Exchange broken links since the culprit was a UX Exchange link improperly translated into a UX.SE one