LOS ANGELES — Some Volkswagen owners say they’re still waiting to complete their buybacks, almost four months after a judge approved a settlement for two-liter diesel vehicles that were part of the automaker’s emissions scandal.Many problems with the buyback program have been ironed out over the past few months, but VW owners who financed their cars through third-party lenders, such as local credit unions or banks, say they’ve experienced lags in response from the company.