rel="external"/data-ajax="false" is not a solution.
It's a poor hack that is way too often suggested as a "solution" to problems that developers have created for themselves by plowing ahead with a project before understand the JQM document structure. It is a way to save a site that was developed in an incorrect way for no good reason to be somewhat usable.
The proper solution is to change the site to not put multiple pages in the same document.
If you can't afford to take the time to apply the proper fix, at least don't do this on your next project, and save yourself this unnecessary headache.
Multi-page documents were intended for very small sites that can be contained in a single document. If you cross into or out of a multi-page document with a link, it is as if you are going to/from an external site. This does not create a good user experience, because there is no transition, and the entire JQuery Mobile framework has to be reloaded.
The JQM documentation does not overly emphasize this approach, so I do not understand where the fascination with this flawed approach to developing JQM sites is coming from. I suppose some third-party vendor or popular blog uses the multi-page approach in a sample or tutorial, and it's been hoodwinking developers into this approach.
I would love to know just where developers are getting this approach from, so that an effort can be made to correct it, and avoid unnecessary problems for developers.
Unless you can fit your entire site into one page, and unless you understand all the drawbacks and limitations of that, and unless you throughly understand jQuery Mobile's document structure and use of Ajax, you should not be creating multi-page documents.
I suggest this means you should almost never put multiple JQM pages in a single document.