I use RS Form Pro in every site I build and use that component nearly everyday.
I am familiar with many of the advanced features of RS Form Pro, such as integrating paypal payments, multi-page forms, and dynamically added fields.
If you send me the website URL where I could check it out and get a better idea of what the issue is, although initially I already have a few possible ways to address your issue.
(The simplest possible solution would be to create an anchor at the top of the page and redirect the URL to that anchor on the Success page.)
I understand a few other designers failed to fix your issue, so it may be more complicated than my initial suggestion. However I am confident I could find an appropriate solution, starting with the simplest and progressing to more complex ones if required.
Thanks!