In case it shall appear at any time that any bond made as herein provided has not been executed by the owner or owners of the property described therein, or that for any reason any such bond is invalid, or that a sale in accordance with its terms would not convey a full and clear title to such property, then the person entitled to collect and receipt for the payment of the original assessment, or his assigns, shall have the right to foreclose the lien thereof for any unpaid portion, as such lien was originally imposed and such lien shall continue until such original assessment is fully paid.