All possible margin call conditions?

When playing around with different strategies I noticed that Zorro sometimes declares a margin call even when Equity is not even close to hitting MarginVal. Am I misunderstanding some of the margin call conditions Zorro asserts?
What are all possible circumstances under which Zorro will declare a margin call?

When Capital is set and you open a trade with not enough equity left to cover the margin cost.

Thanks, yes that makes sense!