Here is the package with heightmap device initialized to QColor(127,127,127,255). Though I don’t think that will change anything, because this device has alpha channel and before the patch the default pixel was totally transparent and the lightness application formula discards fully transparent pixels (by premultiplication).
Btw, @Voronwe13, do you know that we have a new way of building Krita on Windows that lets you skip building all the deps by reusing prebuilt ones from the binary factory? Here is the link.