If I move supplier who is responsible for any smart meter malfunctions

When switching providers, the smart meter will take a little time (could be a few weeks) to connect correctly to the new supplier. 
In this situation, it is not malfunctioning but simply re-synching to the network with your new account details. 
As Blastoise explained, any switch of provider moves the meter to the new supplier’s responsibility. 

Hey ​@geogeo 

Sorry to hear about the issue you’re having but I’m glad to see a couple of our volunteers have already stopped by to advise on this. They’re both correct, and only the current supplier is responsible for the meter, so if you’ve switched away, then your new supplier is responsible.

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As BPLightlog also mentioned, the meters can take time to settle back down during a switch, what is the issue you’re experiencing exactly? 

There’s a handy article here about switching away which may be helpful.