I can't quite work out what is going wrong here. Either the portal is supposed to vanish after you complete the quest, so you can reach those two chests. Or the portal is supposed to remain after completing the quest (with access out of the grove through Sanguine), but the limits of the portal entrance are incorrect meaning you can enter the portal from the room below and therefore not gain access to those two chests. Also Sanguine is found outside the portal after the quest has finished staring at the wall not doing anything, which just feels really out of place and I get the feeling he shouldn't still be there.