Actually it could be as simple as when they were created an error occurred in the database in which case you can just delete and remake them.
Given that creating a new post doesn't have this issue, its safe to say the issue is isolated to just these 2 posts as my test post below doesn't have this issue.
I took a copy of your database and installed it locally, where I could see the problem with the two posts you mentioned, and also, as Shane describes, that there are no such problems when adding new posts.
I checked in the database tables for relationships and was able to see that those two problem posts have existing connections to stad posts, but those stad posts have been trashed, and that is what breaks the UI for related posts when editing the vakexpert posts.
It shouldn't—we should handle that scenario properly—but it is the cause. You can fix the problem by going to the trash for stad posts and either deleting the trashed posts or restoring them.