Possibly a hairy bee fly, except that it had distinct markings on the thorax. The fly was observed for around 2 minutes and it was noticeable that its wings were never still and moved so fast that the camera/flash didn't highlight them.
I sent the fly into David Yeates at ANIC where it was identified as a tangled vein fly by his PhD student, Xuancun Li, who is doing a PhD on Nemestrinidae.