what is the best way to stop roof tile slippage at valleys

Roof valleys often leak because of a common defect.
There are no National Construction Code requirements to stop tiles from slipping at valleys. So, what do Aussie roofers do to correct this defect?
The valley clip.
This metal contraption can be quite effective if installed correctly. But it is far from perfect.
So, are there any other ways of anchoring roof tiles at valleys?
We explore this question on this Roofing Portal video.
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