My vitara is slightly older than yours (2016), I replaced the USB socket for £65.. seems to work every time after that. As you're still under warranty... take it back to them!
A genuine apple cable also helps!

 

It's still under warranty don't play around with it or you could end up voiding it . Take it back to the dealer.

 

I’ve got a different issue in that my Apple lightning cable is stuck in the USB port. I’m a bit reluctant to squirt WD40 in there as I suspect it’s one of the connecting pins that’s pinged out somehow (it’s absolutely stuck fast). How do you get the socket out ? Is it just brute force over ignorance ?

 

Hopefully this works, not having posted on here meaningfully before ... have a look at 2016 Vitara 1.4 S Adventure

 

Popped out the USB socket yesterday and freed the cable. Gave it a liberal coat of contact cleaner and worked the cable in and out a few times And all seemed good. Was just about to refit it and the damn thing stuck again. Looking at it there’s a bit of discolouration rather than scoring but I needed to install an Android cable for my wife and that seems to work fine so I just need to source a replacement Apple cable.