A couple of things good be done to help.
Firstly the mast step might need to be put slightly further forward to keep nose down.
Secondly try not so much "canter"... meaning leaning the mast too far to windward, try standing up more vertical... this is a subtle difference but keeps board down rather than generating too much lift upwards (like a kite)

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Thirdly at Botany, if you are near the runway don't underestimate the effect from the planes as the wind swirls and bounces vertically as well as horizontally over a long distance.
Lastly... your foot straps may be placed too far back. One hole makes a difference.
All these factors could be the issue or a combination of them.
Hope this helps
Fez