Vine Dieback

[SikeandKari]

Hope I'm not breaking any rules by asking two questions at once but the vine on the terrace - which since we have only been here a few months we have not seen in the summer before - has lots of vigorous growth on it but several apparently healthy new shoots just suddenly shrivel and die. No sign of disease or pests that I can see, the behaviour is almost as if the shoot had been severed at the vine (which it hasn't). Any ideas? I have sprayed with copper a couple of weeks back. Some bunches of grapes already forming. Ta for any help, Spike