I think everything you're seeing here is the result of 2 known issues with the Android app. 'Server Error'/'Error Loading Data' and the blank Arduino dashboards are all the result of a server change we made last month, which broke the Android app in unanticipated ways. We are currently testing a build that should resolve these issues, with a planned release date on Monday, March 6. I'll be sure to update you and this thread at that time, and there will be an official announcement thread on the forum as well.
In the meantime, as you've discovered, many users are able to temporarily work around this issue by force stopping, then "Clear Data" on the Cayenne app from the Android application manager. We are aware that closing the app will trigger this bug each time, so we recommend to background the app rather than closing it when you're not using it to try to avoid a re-occurrence of the bug .
The issue with the widgets re-ordering is an older known issue with the Android app. It's being worked on in development as well, but I'm not sure if it will be in the Monday release. The 'Server Error' issue is much more severe and we don't want to delay its resolution by trying to include other bugfixes in the build.
Thank you for your detailed report on these issues, and apologies for the current state of the app. We're working hard to get these resolved for your so you can get on with using the app as it's behaved in the past.
Please know in the meantime as well that the Cayenne web dashboard should have none of these issues and should allow you to use your Cayenne account with less trouble until the Android app issues are resolved.