Questão jurídica principal
Whether the joint parental custody had to be replaced by sole custody for the mother due to changed circumstances and the child's welfare.
Decisão extraída
The conditions for altering the existing custody arrangement were not met; joint custody remained in place.
Fundamentação extraída
A change requires both a substantial change in circumstances and that the modification be necessary for the child's welfare. The cantonal court reasonably found no essential deterioration in parental cooperation and no compelling child-welfare reason to abandon a functioning joint arrangement.