There is nothing wrong with your setup, it happens even with real viewers too, the views will come back on the 4th day or 5th day sometimes if everything is good with your system, do some engagements as real people do to fix the 24-hour drop. In short, if you comment, like, etc other videos from those accounts, it will get fixed.
You can also try watching random videos before and after the target video.
I think the 24-hour drop is related to session length and account engagement types. It can happen when you open the browser, watch the target video, and close the browser, it's not the actual user behavior or it can not be the same for all viewers.