Issue with creating hyperlinks in Markitup editor

Hey,

When I highlight text in the editor and click the link icon, the dialogue window only appears occasionally and randomly. Most of the time, it doesn't appear at all. The outcome is that I can not create links in the editor. Hopefully there's a fix for this without having to reinstall the editor, as a lot of site content has already been generated by my client. Has anyone else had this issue and know of a resolution?

Thanks