[Haskell-cafe] caching ~/.cabal with github actions on windows

I can't get this to work. It works perfectly fine on Linux and MacOS but on Windows cabal always re-builds all the dependencies. The cache post-action on Windows tells me that the cache hasn't changed, which means cabal actually re-created the ~/.cabal directory exactly as it was in the cache! Is this a known bug in cabal on Windows? Does anyone have a work-around? Cheers Ben