I have noticed, that if on server current map has been put in specific folder (for example: beta/shock.bsp or pgp/shock.bsp) client still tries to download it, even if the map IS present on the disk (just not in the matching folder, like there is shock.bsp in maps/, but not in maps/beta ot maps/pgp). This introduces unnecesary load on server and I suggest some kind of check, whether specific map is present in any location in maps/ and not just exactly matching one.
I don't know if it's bug per se, but redownloading in that case is certainly unnecessary and unwelcome for server (for client too, cluttering maps/ folder, but it is of secondary concern).