Problems with Video /Audio Sync in Galaxy J7, what can I do to fix this?

[AC Question]

Problems with Video /Audio Sync in Galaxy J7

I have Galaxy J using it for last 5 months, recently observed that the whenever I start playing Video, it starts normally but after few seconds it gets in slow motion at the same time sound played normally. After this point video progresses at normal frame speed but now the Audio & Video are out of Sync.

Please guide whether this is a virus problem or RAM issue or anything else.

Thanks & Regards
Anand