Since the 3.x version, this game flags activities with a 0 if it's not done or a 1 if it is done. For example, version 5 is eventhack5_xx". When raising Sandra's levels, he adds "if eventhack5_xx == 1 and eventhack5_xx == 1 and eventhack5_xx == 1" and so on. What's happening is you've likely missed an event to flip a switch on an event. In order to fix it, follow Sandra throughout the day and do all her interactions. And look for her at 2400 where she'll likely be in the kitchen. Don't forget the dinners and breakfasts. It's super important for her early on. Be sure to visit the girl's bedroom during the time they are at school since you need to take Sandra's panties.
With Amy, always knock on the door, do the dishes while she is at school for her, then help her with the dishes and homework after dinner. That will keep her happy. Version 5 mostly focuses on the swimming pool and then the homework and dishes events after dinner.