Rodgers1975b83for a list of recc. reading inducemus here.
Cam200130after Rose & Müller-Strübing 1867 304.
Rodgers1975aad loc. attributes it to edd.
Svennung1935556; we might add that eos may have been added as a gloss prior to the text reaching Isidore thereby bringing about the corruption to eostros as Svennung posits.
Rodgers1975b71; it has also been suggested (Svennung 1935 556) that Isidore may have altered the spelling of oestros/eostros to costros so as to enhance his explanation of Latin’s derivation of castra from Greek: if this is the case I see no reason why eos needs to have been present to cause the corruption to eostros in the first place as a wilful alteration is as straightforward from oestros as from eostros. Either way I think this unlikely and overcomplicating.