The Dredge Commissar event gets derailed at the Fridgardr lodge. At some point, the dredge or the humans just stop trying to take it over. Since this POI is involved in the Commisar chain, it is an issue that impacts quite a few people. To get a better idea of how/when this happens, please visit the Blackgate server where this event tends to bug a couple days after server/patch updates are released.