It is true that the Quark Wallet for android has been updated by Hash Engineering (as that is me).  Many users have reported several problems such as freezing screens and on older android devices the app never syncs with the Quark Blockchain (meaning it takes forever).  For instance on my own Android 4 and 7 devices (app installed on June 21) it has been nearly two weeks and it is only at block 3 million.  This could be fixed with an update to the app by building a checkpoints file.  Unfortunately, building of the checkpoints file (requires downloading the blockchain from a client on the same machine and saving headers to a file) is also taking forever on both of my development machines.  Based on my own work, I don't know if new users can get this app to work.

If Quark is changing to a POW/POS hybrid that will definitely break the app if it isn't already broken.  The app will not support any POS blocks.  As soon as one is included in the blockchain, the app will reject it and the app will be stuck on the previous block.  Fixing that will require a ton of work (it has been done by the peercoin developer), but it requires a special block explorer (also made by the peercoin wallet for android developer).  Hash Engineering will not be doing this upgrade.
 

The bottom line is that given this knowledge, users should transfer their coins from the Quark Wallet app to other addresses maintained in other Quark wallets.

In the near future I will be taking the Quark Wallet app off the Google Play store to prevent new users from losing coins.