Electronic issues

I have had a fault with my s3 8v. I opened the car turned the engine over a urgent brake fault came up engine turned off and all the windows came down half way followed with numerous light faults coming up all at the same time. Tried to turn the car off and on but would just repeat the same issue. The car was completely locked out. The AA came out the car wasnt reading any faults and he had to do a master reset of the battery.

The screen for the multimedia system also just randomly shuts down every now and then any ideas?

Thanks

Chris

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