The breakpoint for the cards is ok now. It’s now set to 576px.
The difference is, that card 2 and 3 have an empty excerpt metabox. The arrows work then as expected. I tried also to change the type from page to post, taking out the code used to call the excerpt metabox on pages, but the result is the same.
In alternative, would it be possible to define the complete excerpt text as link?