Not necessarily. Besides, if the I-129B is denied (this was not an error on the part of USCIS) , you will have to refile anyway. You have no way to know if the signature was the only issue. Signatures are normally checked immediately after receipt of the form. Once they discovered the missing signatures, they, likely, stopped processing it.
I'll ask again.....who is the petitioner (US citizen) and who is the beneficiary?
$680 vs $800