i checked the nr of followers in a excel sheet, massplanner shows that i am following the same amount every day. - you mean you checked in Dashboard>Statistics right?
When i use the ‘‘unfollow all users’’ option, it still unfollow only after 3 days(thats my setting) of following that user? - regardless of whether you have the unfollow all users checked or unchecked the Unfollow items after a minimum of x days still applies.
I would advice you to try different sources an settings a week at a time too see which ones work best for your niche.
Using the same settings and getting a good follow back rate for a few days and then not changing anything and getting lower follow back rate can happen, you could try to give it some more time see if it gets back up, it could be just an unlucky few days.
I am having a similar problem with one of my accounts
Despite having chosen to follow 1,200/day and unfollow after 4 days, I just saw that I have about 500 followings, which is impossible without unfollowing immediately.
Either something’s wrong with my settings or with MP, but I am gonna contact support and clarify this today.