Been getting the error:

widgets.js:2 Uncaught Error: No store by the name 'epi.cms.contenttype' exists.
    at Object.get (widgets.js:2:507818)
    at Object.postMixInProperties (widgets.js:2:174700)
    at Object.create (widgets.js:2:15180)
    at Object.postscript (widgets.js:2:14925)
    at new <anonymous> (dojo.js:15:41540)
    at Object.buildNodeFromTemplate (widgets.js:2:59333)
    at Object._createTreeNode (widgets.js:2:59530)
    at Object.<anonymous> (widgets.js:2:466544)
    at dojo.js:15:30941
    at Object.getRoot (widgets.js:2:133158)

When trying to select a page or media from the EPi.CreatePageBrowserDialog. The screen loads but clicking on any of the '...' buttons causes the issue. The link editing in the main CMS edit section seems to be unaffected.

It is affecting Social Reach as well as some custom UI sections we've created in a client project.

Solution is running on CMS version 11.20.10, with EPiServer.Social 3.1.0.

Was wondering if anyone else has experienced this issue before and may know of how to easily resolve it?

I'll be investigating again next week, and may get a chance to compare on CMS versions not running such a recent version, but my efforts to find any info on this so far have drawn a blank.