Rendered retaining wall flaking and render coming off

Hi,

The rendered wall at my backyard is almost 10 years old. The textured paint is flaking at few places and render is coming off at few places. At some places I can just scrape the render and it comes out as powdered (like cement) but at some places the render is as good as new. Is it that some areas are moist and some areas are not? or is it due to weather and ageing? or was the render not done properly? all of them are in the backyard and there is no roof or anything, they get full sun, wind and rain. what should I do? Do I scrape off the loose bits and patch it up and then repaint it?
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looking at it there isnt a key on the first coat of render to bond the top coat one and the mix looks to strong.
id jet wash/scrape off the walls SBR slurry coat it then re bead and render it
or use a thin coat system over the top or a mono render saves painting it..

If you just wanted to patch it then agen scrape/jetwash the walls then paint on a slurry coat on the patches then apply a 511 top coat sponge finish then pain

Some areas where it has bubbled up if I remove the bubble there is some white powdery stuff inside and when I clean it up the render is still there and does not come off so do I need to patch it up or chisel it out? there are some ares where there are few bubbles and some areas where there are only one or two bubbles and then the area around those bubbles are quiet good, even the paint how do I go about it?