In NLRB v. Patent Trader, Inc., 426 F.2d 791 (2d Cir. 1970) (in banc), there was both passage of time and "repudiation" of the union by a majority of the employees.
Enforcing bargaining order and extended certification year to remedy surface bargaining, despite employer's offer to prove that it had engaged in good-faith bargaining prior to Board's decision