There's a good chance that it's a Firefox plugin, rather then Firefox itself.
The only plugins running are Shockwave Flash 19.0 r0 and PDF-XChange Viewer. To be honest, after updating Firefox (now version 42.0, I believe) it seems a bit buggy when working with MODX. It doesn't accurately detect when a page/resource has been altered, and with non-altered resources when I click to navigate to a different resource Firefox shows me a popup about saving data before moving away from the resource.
Anyway, not to worry. Now I know it is a caching issue with a particular browser, I can warn the client and there shouldn't be a problem.
I've had issues with the latest version of Firefox on several non-modx sites. I haven't noticed anything on a MODX site, but it wouldn't surprise me.
Is there a tag that displays the TV's content?
You might try switching to pdoResources (in the pdoTools extra), though I'm not sure it will make a difference.
You're not using CacheMaster by any chance?
Create a snippet with this code from your TV (reformatted -- it has to be on one line in the TV):
Put a tag for it on a page and see what it returns.
That looks about right, though you haven't said what you mean to do with that data. If you just want to show a list of links to those pages, Wayfinder might work a lot better.
If necessary, you could use TVs for the values above.
The rowTpl would look something like this: