Gearbox chatter or something else?

Dear members,

I've been hearing some chatter/rattle from the gearbox or clutch of my 1.4mpi 8v (002 gearbox) since 2012 (now only louder in 2019) when the car is in neutral, pedal released/clutch plate engaged. This chatter goes away when I depress the pedal/release the clutch plate. This sound can only be heard when the engine is warm.

* No other strange or really distinguishable sounds while driving or shifting gears.

* No rattle while driving as slow a possible in 1st gear.

* Clutch plate friction test passed by pulling up from stop in 3rd gear at 2500rpm (at max torque, no sweat).

* Transmission fluid was replaced every 5 to 7 yrs, no leaks.

* Clutch pedal biting point, smoothness or travel (more a complete journey) never changed in 15 years.

* The car sometimes has shifting issues, but these are very possibly related to 5 to 10mm play in the shifting mechanism from neutral to the 1/2 gear pos (gearshift lever on the top of the gearbox was locked with the plastic pin during this test for play > the sliding shoe (6Y0 711 550) is pretty and mostly worn). I'm going to fix that a.s.a.p by replacing most plastic bushings, catches and the shoe of the shifting mechanism.

All together: Is this the normal gearbox chatter sound everyone is talking about, or is this a bearing or clutch disc springs rattle issue from your experience? (car now has 120k km/19 yrs).