Kate
My understanding is that only members of the EC can demand an EC meeting be held and at least one-third of EC members (not owners) have to be in favour.
When it comes to Extraordinary General Meetings, at least one-quarter of owners (by unit entitlements) has to support a call for a general meeting.
An owner, could, theoretically, call a general meeting, sack the current EC and install another one more sympathetic to their cause(s). Actually, it's more than theoretical – I've seen it done.
But it would be easier for them to get the required third of the EC onside and do it that way. An individual owner can't demand either an EC meeting or an EGM.
The question of owners being unfinancial is a tricky one. They could, I'm thinking, get enough support to call an EGM and then not be able to vote at it (and, yes, I've seen that done too).