If the files aren't in the sv_downloadurl location or if it's disabled the server will instead attempt to upload them on it's own at it's slow rate.
That being said its seems your models aren't in the proper location. Double check that they are in the proper location. If you have no clue take a look at the plugins code and check if the files are named properly along with it's location ie: cstrike/models/player/subfolders if any.
Look for a line like this within the plugins .sma file to confirm.
PHP Code:
precache_model("models/player/example.mdl")