The second time losing his memories is a shared dream they both had during the coma, after the guiding session because Kwonwoo became stronger after it and Dowon was suffering because of the need to give more guiding and the risky treatment. It was a reflection of Dowon's trauma about being forgotten and a way to development for him to fight for himself and their relationship, and also not accept being forgotten by Kwonwoo a second time.
Because of their imprint their dream was shared and revealed both of their traumas, Dowon had a quite nice life before meeting Kwonwoo (lol) so being forgotten and his guilty conscience of believing he is the cause of Kwonwoo current suffering (also the belief that he would be better without him) is his trauma.
They made it much more confusing than in the novel. Also, the story is a bit more longer than the manhwa (They communicate more and it's mostly in Dowon's point of view, also, the lack of communication is shown as a problem they try to solve together) but i do believe they'll make the side stories too.
Can someone explain what happened from the point where kwonwoo lost his memories a second time ? It should have just ended before that? It was peak? Now they like, can’t be together or something because dowon took some medicine but he had to take it so they could ? Nothing worked and now they’re both disabled ? Girl