"This afternoon's race started well with me, holding second place for half...until I was pushed wide coming onto the back straight," Gibson said on his team's Facebook page.
"As a result of this, the freight train of Ssangyongs raced past me and I dropped to back to seventh.
"I fought my way back to cross the chequered flag in fifth place."
Gibson wanted a strong finish on Sunday, but did not feature on the podium with Race 3 being won by Bennett, ahead of Taupo expat Kieron Rollinson in a photo finish with Connor.
Connor finally cracked the top of the podium in Race 4, winning it from Orr-West and Royce Rollinson.
"The racing today wasn't the best for me with a eighth and a 11th," said Gibson.
"But that was enough to finish fourth overall in the championship in our first full season.
"A great finish for a busy year of racing."
The results ensured Connor won the season title after six rounds, which also began at Pukekohe last November.