GAURAV1113 - thank you for being a student. I apologize for this issue you are facing. From our internal testing, we have discovered that all files work fine on mobile provided you start them afresh. While starting afresh, all the animations, the audio, the in-place quizzes, and the logic on the result screen works perfectly.
The only issue we have been able to replicate is one in which you "resume" a file rather than start it "afresh". This issue impacts fewer than 20% of the files and we are working actively to fix this. Therefore, I would recommend that you don't "resume" the files, rather than start them afresh. This will ensure that you are able to study un-interruptedly.
What caused this issue?
Every file that we published worked perfectly at the time of release. However, updates to the HTML5 standard have impacted the "resume" functionality in some files.
We do have a fix on the issue and shall be deploying it in near future. However, to ensure uninterrupted learning, make sure that you start files afresh until then.
I hope this helps!!
Regards,
Rajat Sadana