Replacing hyperlinks

Hi, just a quick question; I'm adapting a course created by someone else (we have different language versions of the same course for the project I'm working on). When I update the hyperlinks to new addresses and preview the whole presentation they still direct to the old pages. The url hyperlinks I addressed by completely deleting the original shape and starting again. But after deleting a redundant slide, the buttons to other chapters in the course are all one slide out. When I try to fix this through the hyperlink settings they are still pointing to the right places. Was wondering whether anyone has come across a similar problem? Thinking it could be a problem in preview that would be fine when published...but would hate to publish and find it still doesn't work, or painstakingly redo each link if there's no need!

Any suggestions welcome!

Thanks