On the rare occasions when this has happened to me, and when all sensible efforts have failed to resolve, I break out my fiber reinforced packing tape and run a strip tightly around the rim. Then run your preferred rim strip on top of it. This has always fixed things for me. The downside is that the fiber tape may be difficult to remove if you need to.
Also, Rema TipTop is a patch system that you can rely on.
Good luck.