Ancien Maestro, I suspect legal departments do not adequately review all adjustments to receipts. And even when they do review, they may not be thinking about the right problems and potential problems.
I believe a class action suit here would be difficult. Though I do practice law, including some work in plaintiffs-side class action matters, I am currently preparing a complaint to US DOT ACPD and I do not currently envision class action litigation.
Still hoping someone will chime in by email or PM with some receipts!