Why can't I accept changes after auto schedule

[Marcel Rietveld]

Hi all, I have noticed strange behavior in Jira advanced roadmaps lately. When I try to auto-schedule only a relatively small number of epics and stories get updated (i.e. assigned new dates and are shown in the blue striped color) while the rest of the epics and stories are not updated and are shown in grey. When I click "Accept Changes" nothing happens. When I click "Cancel" the changes are reverted back. 

Yesterday evening I noticed this behavior. After much trial and error I had to let it go and stopped trying. This morning I tried again and it worked. And now it has stopped working again. 

This morning I also added some sprints in Jira; before that AR seemed to work fine, after that autoschedule in AR didn't work anymore. 

Am I doing something wrong? Do other people recognize this?

Any help is greatly appreciated. 

Thanks,