I would worry that as part of the retaining wall is in such poor condition, the rest will go the same way with a risk of the land behind it collapsing. I believe that in the UK at least, the owner of the land that's being retained by the wall is usually responsible for its upkeep so if it's someone else's land on the other side you should have a word with them.
Doncaster, South Yorkshire. Soil type: sandy, well-drained
Step one: Fix the drainage problem. You need to stop water building up behind the wall and find somewhere for it to go. Any patch job will blow straight off if you don't.
If you can keep your head, while those around you are losing theirs, you may not have grasped the seriousness of the situation.
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Having turned the pic - is that another wall just in behind that [horrible] line of timber edging? @poultonj14-C20kxha
I live in west central Scotland - not where that photo is...