The problem with fixing into a rendered wall is that you can't see what you are drilling into, e.g. what's behind the render. You can tell what sort of sub material by the colour of the dust but you can easily drill into a mortar joint.
You drill a hole, inject this sort of thing;
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And insert one of these;
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The resin sets in 20/30 mins & the fixing is incredibly strong. No stronger fixing is available.