I've check both L and W's profiles. Both have Snapchat allowed in Playtime and both have a significant amount of Playtime set during their rest days which would allow them to Snapchat during this time. Can I confirm whether you mean that you set their profile to Sleep or Rest?
Rest Day (Day type): Weekend day with a more relaxed schedule made of usually Sleep and Play times only.
Sleep (Routine type): A routine in which by default, no internet content is allowed
We may need to do some live troubleshooting over the phone to determine the issue.
If you could give our support line a call on 1300 398 326 or book call back with us by clicking here, one of our support staff will be happy to assist.
Currently we only prevent applications from connecting to the internet, we have no way of stopping them from opening and watching downloaded content offline.