Xanadu applies Target Lock on opponent Xanadu during attack on HT

Maybe it is only in specific circumstances. For sure:

 1. HT and XB on opponent board

 2. Attack with my XB basic on HT (opponent XB does not have any debuff)

 3. Double tap from my XB

 4. Target lock appears on opponent XB on second shot

 5. Always before 1 available reinforcement 

 6. Happened on bluestack and Android phone (it is not platform specific))

I am trying to take pictures before and after on next appearance.