When will a court change custody on an interim motion?

And in Southorn v. Ree, 2019 ONSC 1298, McDermot J. made the following observation, at para. 13: It is presumed that where parties have agreed to a time sharing arrangement, that arrangement best reflects their initial assessment as to the best interests of the children. Moreover, to change custody on an interim motion runs the risk of the child going through two changes of custody: one after the interim motion and another at trial. That would create more, not less, instability in the child's life. Moreover, evidence at a trial has the benefit of being tested through cross-examination whereas evidence at a motion is by affidavit where conflicting versions of the truth cannot be determined with any certainty and the court is unable to make credibility findings.