It's a new playthrough. Also, I did as you suggested. Loaded an earlier save and replayed it from there again. Now, before I went to give the leaflets and thus met Megumi first. This time I went to the workshop and met Mei first. Curiously, by the end of the dialogue of her first meeting, the same kind of bug happened like with Megumi previously. After the conversation, her image would briefly appear when changing locations and when I went to the beach, the same exception screen with that same missing file happened. I rolled back, went to sleep and next day managed to do the leaflets thing and get to the beach without an error and got to the Megumi scene. But it resulted in the same bug. Now, sometimes going to the beach doesn't cause the exception, but sometimes it does, seemingly randomly.