BUG: Server Member count is incorrect

I manage a community server and I've noticed that the Server Insights and Server Members page display wildly different member counts. 

I realise that Server Insight is two days behind - but trust me, we've not gotten 500 new members over two days. I've noticed the discrepancy has been like this for a while. 

We recently did a rather big prune - I am guessing this might've been when the numbers got all whack, but I'm not sure.