A poll states '1 member has voted' but then shows that 2 members voted: 

Would suggest ensuring you're on the latest release, an unmodified theme, and do not have any third party add-ons related to polls. 

It is also worthwhile knowing when this topic/poll was created. There was a bug quite some time ago with something similar when it was possible to edit the number of individuals who voted. This capability has since been removed.

If after doing the above, this is still present and it is not an old topic/poll, we would need the topic URL.

13 minutes ago, Jim M said:

Would suggest ensuring you're on the latest release, an unmodified theme, and do not have any third party add-ons related to polls. 

All of this was the case, yes, however now the problem has sorted itself out (there are now 4 members who have voted). 

I assume maybe some kind of caching issue? 

Some info might also be updated via tasks that may had not have had a chance to run between the time it occurred and when the update task ran as well.  

9 hours ago, David N. said:

I assume maybe some kind of caching issue? 

It would certainly suggest so. I can only say to let us know if you see it happen again at this point

Will do, thank you.