I tested it today. Even if I change the package name, it is still detected as a "Suspicious file detected - Cloud Reputation [Susp]". So it's not related to the package name.
I also compiled an APK, then sent it to another test phone I have, that have the same Avast version, and installed it from the SD card. It was also detected as suspicious. So even an APK is detected after installation. So that means that they will get the problem if they install a new APK version from Google Play.
I'm delaying my app update and really see it as a problem... I reported many compiles of different projects as false positive but nothing seems to change on Avast side.
In fact, I installed a build I did 2 weeks ago and it got flagged. I reinstalled my previous version an it did not. Something must be flagged in recent compiles. Otherwise, it would have detected it from old compiles... Or maybe it is something updated in SDK manager... I recently updated the Android SDK Tools, Platform Tools and SDK Build-Tools to the latest version. I downgraded the Android SDK Tools, Platform Tools and SDK Build-Tools and it did not make any difference.
I'm puzzled as to why this is happening...