For what it’s worth, our strata development had a brick retaining wall that had a bit of a lean to it and had had for quite a while. We got an engineer to look at it. He advised that it was not unstable or unsafe and might be fine like that for many years. He advised how far it could go before we would need to worry about it. We monitored the lean at several points with a plumb bob several times a year. For most of a decade it barely moved but eventually it reached the point where we had been advised that we would need to rebuild it, so we then got a builder in to build us a new wall at that time. We now have a nice straight wall.
In short, fix it if an engineer says it is unsafe. Save your money if it is not unsafe.