Hey Tim,
I help with Joe’s support and he sent me your project file and it previews beautifully on my computers as well. Here are some screenshots from one of my iMacs.
Since it works on both Joe’s and my computers, it seems like there is something with your version of RapidWeaver. Did you upgrade from a previous version or download a new version from Realmac when you updated to 7.5.1?!?
Maybe the people at Realmac can help out here as well. @simon @dan @ben @Aaron @LaPan any ideas?!?
@TimLawson can you create a new project file, then drag over the pages from the current (old) into the newly created project? Be sure to apply the correct theme (etc).
Save as a new name to a new destination (Documents / Desktop, etc).
Does the preview behave the same way?
@zeebe Hi Rob - yeah - we’ve chatted before. Thanks for your help and @joeworkman’s too.
@Aaron - thanks for your response. Starting a new project and dragging the pages in from the existing one makes no difference to the outcome in Preview. 
I have also deleted RW7.5.1 from my Applications folder and replaced it with a new copy downloaded from the RealmacSoftware website. Sadly, that makes no difference either.
I have started a completely new project with a single page Foundation theme. I’ve added only a ‘Site Styles’ stack, a ‘Paragraph’ stack and a ‘CMS Core’ stack. I have not changed the default settings in any of those stacks. I can preview the ‘Paragraph’ stack perfectly - just as expected - but the moment I add in the ‘CMS Core’ - kaboom! - I get the same issue as previously described - loads of “gobbledegook” in the ‘Preview’ pane. @zeebe? @joeworkman?
Hallelujah! I’ve got this fixed…
I removed every single reference to RW7 on my computer (using ‘AppCleaner’) having first copied all those files to a folder on my desktop - see screenshots below (in case it’s of use to others). I reinstalled RW7 from a fresh download and then restored all my stacks, themes et al to their original locations using Time Machine and now preview of TCMS pages in RW7 is working “like a dream”. (Of course, I’ve had to insert license details here and there for the app and for Stacks etc. but that’s no big deal as I use 1Password to store all that information.)
Many thanks to @joeworkman, @zeebe and @Aaron for your help and patience with this - it’s much appreciated.
Best,
Tim.
