Stateful snippets redirectTo ultimately relies on:

 private[http] def appendFuncToURL(url: String, funcStr: String): String =
  splitAtHash(url){to => (if (to.indexOf("?") >= 0) "&" else "?") + funcStr}

the problem is that the actual URI is lost and if you try redirectTo("/homepage") it actaully sends you to /?F1089777327057MDT=_

the fix is:

 private[http] def appendFuncToURL(url: String, funcStr: String): String =
  splitAtHash(url){to => to + (if (to.indexOf("?") >= 0) "&" else "?") + funcStr}