In previous version of sketch we could maintain scroll position in an overlay. With recent sketch update that option is now only available for screen to screen navigation in a prototype.
Use case: Panel overlay with content that user needs to scroll. ie. Menu items.
When user clicks on a menu item and navigates away from screen to another. Panel overlay should maintain scroll position so when the user reopens the menu it is at the last scrolled position.
Hey there. 
I’d like to help you resolve this situation, but I’m a little confused by something you said. Even in the past, the option to Maintain Scroll Position has never worked with Overlays, and has only worked on regular Artboards/Screens.
I am sure that I am misunderstanding your situation though, so would it be possible for you to provide an example of one of your documents where this was previously working, and we can take a look at it for you. You can either upload the document here, or if you’d prefer to keep it private, you can send it to us at productsupport@sketch.com
Although some things have changed in the latest version of the app, I am sure that whatever you could do before, you can still do now. No features have been removed. 