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Just to add, if you look at the day view you get a different story i.e. Not all thin lines reach 1/2 SBD

Yes not every day.. but also not random. We just found another clue: it looks like this is happening when the market price is above 0.5

Yes, it's very strange however I wouldn't rule out inexperienced users not understanding the market. surely there must be many new users every day?