I have a Mazda5 GT 2006 manual 5 speed. 1200km

When slowing down in the 3rd or 2nd gear, I ear a rattle noise from inside the transmission. It was not there before. Its like something loose inside the transmission or a gear or a bearing . As soon as I depress the clutch or accelerate, the noise disapear. It happens on a soft downshifting while the engine is reducing the speed slowly.
Anybody encountered this before ?


The problem disapeared by itself few weeks later. (8500 km)