What exactly are you scrolling, the main window or the portal window? Can you post a screenshot of the portal?
Sorry if you are already aware of this, but how large is your portal row? That can affect how many records you see at a time, in a give portal space. Maybe the row is much larger than it needs to be?
There must be something wrong with your relationship. How are your Table occurences linked together?
If you want to list all the patients, why not create a layout in list view mode instead of having the patients in a portal?
I did created a layout in list view mode and now it's works very well.