Brake pedal goes too far but will pump up

This a 2004 Facelift ZR 105 with 42,000 miles.

After about 5 minutes of driving when the brakes are applied the pedal travel is too long although there is some braking effect. The pedal can be pumped once for a normal pedal feel. It seems to need to be driven for about 5 minutes from cold before it will do this and once started it will be it most of the time.

If I start the engine with my foot on the brake pedal the pedal drops down a little as I'd expect as the servo starts to work.

The adjusters for the rear shoes look OK as I've read they can wear and jump.

Any thoughts?

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