[SOLVED] Evo 3 : clicking noise and creaking noise

After replacing the folding pedals with standard pedals and checking that the two bolts that hold the locking latch are tight… is there a simple way to investigate where that creaking noise comes from, such as checking if it’s due to the KS3 gearbox or the rear hinge?

Provided it’s the KS3, does it need to be replaced, or simply serviced at a Strida shop?

Thank you.