Sir,I have cleared the default settings of gallery, due to which the palyback of hd videos started once again. But yesterday i was using bluetooth headset device with this handset. After that i found that the hd video playback with gallery was again giving the same problems. Then as per your suggestion i have i have installed the google photo and set as default player for hd videos. This app did play the videos properly.
I also encountered another issue of non sending of mails from asus mail app after using the bluetooh function. The mail is stored in the out box, even though there is working wi fi and 4G sim internet available.
I hope this will give the insight of problems in the system. Hope you could resolve the software glitches.