"Over time, things became difficult between the head coach and particularly the senior playing group. That was around confidence - things were going wrong, particularly post the Malawi game, things were rather fractured within the team," said Mackinnon.
"The dynamic between the head coach and the playing group over time became problematic. There is no doubt about that.
"The players came to the view that they were off track and didn't know how to get back on track. There was a complete lack of confidence at that point."
Southby's leadership style was pinpointed as the key reason for the division emerging between the coaches and players, with Southby preferring an athlete-led approach, compared with the more dictatorial structure of previous regimes.
"The challenge the Silver Ferns faced is that the athlete-led philosophy tends to work best with a team that is experienced and has leaders ready to step up," said Mackinnon.
"We concluded there was a disconnect with this team - it was crying out for a more hands-on approach.
"You simply had a disconnect develop over time between the philosophy of the coach and arguably the need of the players.
"With this particular team being young and quite green, they were looking for a different type of coach."
The review found Netball New Zealand noticed the problems emerging but their attempted solutions occurred too late.
Mackinnon noted that the organisation "intervened later than we believe would have been ideal".
Netball New Zealand chief executive Jennie Wyllie wouldn't be drawn on whether Southby, who was contracted through to the 2019 World Cup, received a payout on her departure.
"We accepted Janine's resignation and that's all we'll comment on in terms of employment matters which are governed by employment law."