This is in fact not expected behavior and maybe related to OS Version and device only. We'll have a look at this issue in soon published SDK version 2.1.
Meanwhile please try to clean the Wikitude SDK cache manually before entering the AR-Activity using
final String cacheDirAbsolutePath = ArchitectView.getCacheDirectoryAbsoluteFilePath( yourLauncherActivity );
I had a new question about the Android version of the SDK. The 3d models seems to load very well on many phones,but some devices seems to have problems to reload 3d models.
I will tell you the problem :
I launch the app. Models loaded. Perfectly. I click "back" then I relaunch the app, then the models doesn't load and the "onError" event occurs.
Files are stored in assets folder.
I launch the app. Models loaded. I click "back" then I went to "Parameters > Process > Background Cache Process > Delete my app cache process". I relaunch the app. Models loaded.
Same problem occured with the SDK examples.
I tested this behavior on an Acer phone with Android 4.1
Christophe Brasseur