I have just rescued a p11
A good clean inside and out
The rubber? Wheel was very hard and glazed so gently cleaned the rim with emery cloth and then with MEK a rubber rejuvenate chemical
It was quite a bit better but still not perfect.
If i helped the solonoid it was snappy and perfect
Measuring the voltage across the solonids it was only 15v dc and if the reverse solonoid was used at the same time it dropped to 12v
So i added a 100uf cap across the dc side of the bridge rectifier
The whole machine is now perfect