Hi,
I encountered the bug as follows. Please read, reply, and fix if it is truly a bug and not misunderstanding of ruling.

The situation was that I summon my raidraptor force trix. Then, I set my rank-up-magic doom double force down and end my turn. During my opponent turn, he summon slifer (his only monster on the field) and attack my force trix. There are also no other cards which forbidden special summon on the field at that time. However, my force trix just goes to graveyard and didn't let me use the rank-up even though it is quick play spell. The same problem has also happened before with same situation but the attacking monster was a blue-eye normal monster. The xyz I want to summon using rank-up was d/d/d dou-dawn king kali yuga.

is it a bug and not my misunderstanding of ruling??

Hi,
I encountered the bug as follows. Please read, reply, and fix if it is truly a bug and not misunderstanding of ruling.

The situation was that I summon my raidraptor force trix. Then, I set my rank-up-magic doom double force down and end my turn. During my opponent turn, he summon slifer (his only monster on the field) and attack my force trix. There are also no other cards which forbidden special summon on the field at that time. However, my force trix just goes to graveyard and didn't let me use the rank-up even though it is quick play spell. The same problem has also happened before with same situation but the attacking monster was a blue-eye normal monster. The xyz I want to summon using rank-up was d/d/d dou-dawn king kali yuga.

is it a bug and not my misunderstanding of ruling??

It's not a bug, you have to force the activation of doom double force. When your monster is destroyed by battle try to press the A tab. It means "answer" so the rank up magic will trigger

What about for the mobile version? Even when I hold down on the screen,which I believe is the equivalent to holding down the A button, it still does not react.