as you may notice with many many custom maps, is they all have texture read errors... yet dispite this, they still WORK.
the big deal about forest, is that yes there is that repetitive console message, but the map works fine, and i guarantee you will never find the texture that didnt load properly, because the map is too big and detailed to search every nook and cranny for. as far as laggy goes, it is true that some machines have issues running this map because of CSS's render distance and the sheer complexity of the foliage present, however this can be easily fixed in each users graphics settings, by lowering the texture quality, thats all, just the textures. models and shading and all that jazz doesnt need to be changed.