Clonk in to first gear = impending gearbox bearing failure
Here is the follow on from the initial clonk in to first gear I had which lead to an expensive double clutch change, due to a failed bearing.
Below is the symptoms I had in case your car starts doing the same.
The first sign was the car started to make a clonk when first gear was engaged, it had the feel of something moving so wondered about bushes. Did not clonk if the car was engaged in to second or reverse.
The second sign was the car began to judder when pulling away, occasionally noticed the feel of movement when engaging reverse.
The next sign was the judder got worse, this lead me to get the clutch changed, (no sign of slipping) When the clutch was removed the clutch plates were covered in oil leading to an oil seal change.
When the car was returned it felt better however still made a clonk in to first gear with small amounts of judder in first nothing in second.
Not long later however the judder starts getting bad and oil starts appearing around the gearbox housing although its not clear where the oil is coming from
Finally the car has developed a very bad judder in first gear making that gear almost unusable, (fine in all other gears) a horrible smell of burning oil is coming from the engine bay, oil now pooling on top of the gearbox housing.
Fault diagnosed as an impending bearing failure at one end of the gearbox, leading to a strip down and clear out of swarf from the breaking bearing, another new clutch fitted as the oil seal had gone again (due to the movement of the shaft) contaminating the recently fitted clutch.
So if your 916 starts to clonk in to first gear consider an impending gearbox bearing failure, if you are changing your clutch on a now “old” gearbox, and it its contaminated with oil have the bearings checked and for the extra £50 consider getting it / them changed.