Overwhelmed and not concentrating
The dealer (sitting north and inexperienced) put down a pass card and then reached back towards the bidding box. Meanwhile LHO passed. North did not notice LHO's pass and slowly started to pull out a bid and eventually put 2C (23+ HCP) on the table. South stopped himself from bidding his 2H (6-card weak with 10 HCPs) as he was about to and called the director. North said she was overwhelmed by picking up such a strong hand (28 HCPs as it turned out), was still deciding whether it was a 2C or 2D bid, and had not concentrated on selecting the stop card and had pulled out a pass instead.
A. Did her using the term 'had not concentrated' prevent a ruling of mechanical error?
B. As south had deliberately not bid at the usual pace and waited to see what north was doing up, does that affect the ruling?
C. If mechanical error was not allowed, how does south proceed knowing partner has 23+ HCPs.