I experienced this in every mission, you can have several steps in each mission, example, in In Shock you have the first step getting rid of the tentacles of the beholder, the last step, fighting Kuzmann... if the host quit for any reason, if you are in the first step, you have to destroy all the tentacles again, if you are in the last step, Kuzmann has his life refilled... and you can see the same behavior in every mission, that restart to a certain point if the host quit