This camera issue is well known issue and yes it is the issue with Motherboard.
Only option is to give it in service center, it will be fixed without charge if under warranty. if not then they will charge huge.
Service is horrible. i have given my phone two times. first time it took 2 months and then after 15 days only it started giving the same issue again. when i went back they said it is same motherboard issue, so i gave it again. This time it again took more then 2 months. So in 1 year warranty period my phone was in service station for 4 months.
When you give it to service center then dont think when will you get it back. We all should learn onething from this. Stop buying any MI Products. If they dont care about their customer then why should we support them by buying these phones with inbuilt problems.
I have another MI Redmi 2 Prime now that phone also started giving the same error. it is also still in warranty period, so i need to get ready to face the same cycle of going to Service center and waiting for more then 2 months for getting the phone back.
If you are having camera issue and your phone is not under warranty then i suggest go and buy some branded phone and throw this phone, as the repair charge will be approximately more the Rs.4500 (Phone actual cost is Rs. 6000)