@jotamartos
Thanks for your advice.
Basically I don't downgrade the Android version from now.
This critical problem is not depending on my Tablet environment, it should be improved by Opera mini developer.
By the way "Opera" does never occurs same problem.
I really strange for me, why it has been happening even Opera mini has completely uninstalled and reinstalled.
At the result I have already uninstalled the Opera mini. Then I will never use it anymore.
Thanks