Hi db042190 ,
According to your description, when you scroll horizontally to the rightmost side, the report can display fine. But when you scroll horizontally but not reach the rightmost side, there will display some overlay report items, right?
In your scenario, please check if you have specified value of FixedData property as True for those static members in rows groups or column groups. Please refer to this article: Keep Headers Visible When Scrolling Through a Report (Report Builder and SSRS).
If issue persists, we would like to know if you are running the report in BIDS or browser. Pease run the report both in those two environments and compare results. It would be better if you could share report design and screenshots about overlay results.
If you have any question, please feel free to ask.
Best regards,
Qiuyun Yu