What happens if the other parent reports false child protection concerns to try to gain an advantage in our case?

Making a report to a children's aid society that turns out to be false, or made in bad faith to gain an advantage in a parenting dispute, doesn't just disappear once the society determines there's nothing to it - it can become relevant evidence against the parent who made it. Courts consider each parent's conduct and credibility, and the best-interests test can take into account a pattern of using false reports as a tactic, since that behaviour speaks to a parent's willingness to act in the child's actual interests rather than their own litigation position.

That said, proving a report was knowingly false, rather than a genuine but mistaken or overcautious concern, takes real evidence - an unfounded investigation doesn't by itself prove bad faith, since many good-faith reports don't lead to a substantiated finding. If you believe the other parent is doing this, document the pattern - the timing relative to court dates, prior similar reports, and investigation outcomes - and raise it with your lawyer, who can decide whether and how to put it before the family court. Don't let this discourage anyone from reporting a genuine safety concern; the issue is bad-faith conduct, not reporting itself.