OK so on several occasions I’ve gotten a phone call or txt answered or replied to txt come back to game and I’ve lost the challenge map I was playing lost all floor progress. or using a crystal topaz mainly my second ruby I’ve been grinding very hard for, go
same thing…gone…I’ve now lost a ruby 6-10 topaz and dozens of challenge map progress… I’m very upset with the game loosing interest and will stop playing…
There is nothing we can do about this since your phone automatically ends the app. This is a device specific problem.
Your best bet is to turn off your connection to your service provider to prevent calls/texts while you play. Else buying a more powerful phone which has enough Ram to keep DQ in the background is the only solution.
Please Email support they would be happy too get you back any items you lost but as clogon has said what you have described is a phone problem so you will need too properly exit too the main menu before switching apps in order too save your data properly 
Dude you should have used the back up in dq … I thnk it was DQ CLOUD… It will appear when u start the app… Open ur data or wifi first to upload ur acc. For back up… It really helped me when my phone got factory reset… Be sure to upload ur account everytime u make a progress because u might not know whT will happen… 
Depending on device (and android OS version) this is handled differently. Also, depending on the type of message app you use it could force a memory flush as well to make room for the message app. For example snap chat…in some cases if you don’t have enough free application memory (not physical storage…this is different) it will close other apps to make enough room in memory to run the app your are opening.
I like how you use non computer science jargon. I should have done so too.