Thanks for your answer!
Yeah I am using the most recent version of both the plug-in and Pages, the latter seems to be the actual problem. I just found another user complaining about broken in-text citations, I suppose I’ll just wait for the next update and hope for a bug fix. Worst case, I’ll downgrade to Pages 6.1 or even 5 as all was running fine with those.
Very annoying but at least I know what the problem is now.