H4 Drop Box - Visa expiration date

[vishal27580]

Hello,
My Son and Wife went for visa stamping in India (Mumbai). This time we used drop box option.

For my wife and son, their H4 extension (797 and I-94) is approved till 01 DEC 2020
My H1B Extension (797 and and I-94) is approved till 01 DEC 2020.

But they got Visa stamped till 01 DEC 2018.
They will be traveling back on July 27th 2018 to US.

I was wondering,
Is it ok to go for stamping again in person again as Visa is valid for less than 6 months?
Or is there way we can rectify this error?

Thank you