A friend has a Tikka T3 Varmint which is about two years old and by chance he found that when the rifle is upside down, IE in the landrover, and the bolt is closed when in this position, 95% of the time the action is firing.
Luckily the rifle wasn't loaded, but since checking the rifle whenever it is inverted and the bolt closed the action fires.
It appears that the sear cannot engage in this position however if cocked normally and then inverted the rifle can be knocked all day without firing. Has anyone else experienced this. He is going to contact the dealer he purchased the rifle from to get it sorted.