Hi. This rings many bells!! I have been suffering exactly this issue and have been pulling my hair out. I have tried many things to cure the problem with no success. I have been in touch with HH but still had no solution though they did mention this forum and you in one of their general responses. I sent you an email earlier this evening to see if you could offer any help with the issue but have now found this post! I will be checking this plug lead connection first thing tomorrow and it will hopefully resolve this issue.