You know...if you have a gear retraction problem....it's very possible it's just one gear or a stuck door even....your performance may be good enough that it's difficult to even notice except for the red light on your panel....until you get high enough that it's noticeable or you go fast enough that you can feel it.
"Coffin corner" wouldn't be an issue, that's something else entirely and usually not something you think about with modern computer designed wings and not in a straight wing Citation.