So this may not be a bug....may be by design....
Unlike Sickbeard which has it's own set "upcoming" list, Sonarr just has a "Calendar" which allows you to see the current day, week, or month in advance.
Because this isn't defined as a set list I'm not sure how long the "upcoming" list is supposed to look at when determining what shows are coming up soon in nzb360.
If it is only supposed to look to the end of the week...then it appears it is working correctly. But it doesn't seem to look 1 week ahead...only the current week.
If this is normal, then perhaps I should put in a feature request for you to be able to change the "Upcoming" to be day/week/month just like you can in the webapp.
For instance, it would be really nice on Saturday to be able to look at the following Monday to know if another episode of your show is going to air...