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Are the posts threaded through the fence panels?
If they are just wired to the outside, why not just have a whole panel gate, usher the animals in as before, the gate is wide enough so there will be no " corking" as you got.
Once through the animals are going to take off into the scrub leaving you plenty of time to fit the last panel to the fence.
If you need a gate, allow a panel and a gate for the hole, then you can use the post each side of the gate to swing if from and to lock it too.
Just to be a picky bugger.