Ok so I have been trying everything I can think of to solve this.
Today I setup a cocoon account, after I saw that it was one of the build types about to be documented on the wiki.
Success with the Webviewer+ Engine on my Galaxy S5 Mini, but for a 4MB app it added another 24MB.
+++ An Update: The standard Webviewer (not plus) Engine, illicits the same error as Phone Gap.
However there is no screen flicker and the app is working.
I would still prefer to use Phonegap if we can get this screen flickering sorted.
MobileNoob