Yeah i guess cos its bonded you could look to replace both rear stays, but £££s.
Kinda looks like the bonds at the stays have been gunked back together already? And having looked again both are bent, as well as the crack. Looks like its taken a proper impact at the back?
Lovely looking frame but big dent in one stay, and other side snapped above dropouts. Alu frame so KO I think? Shame