When Calva disconnects from the nREPL server I often see this error. Is it something we are doing wrong in Calva, or something wrong in nREPL?
I've never seen this myself, it seems that the socket was closed before you tried to close the connection, which might be the result of a wrong sequence of operations. Might be best to open a ticket in the issue tracker so we won't forget to look into this more closely.
My availability continues to remain relatively low due to the war in Ukraine, but I hope things will improve soon.