Question about Denon Dp-300f

Perhaps someone here has some experience with this: my record player produces an acoustic noise (comparable to a howling or grinding noise) when the turntable is turned. After removing it several times and checking the belt, the noise is still audible. Today I lubricated the belt with WD40 and lo and behold, the noise was no longer audible for a moment (about 1 hour). However, it then reappeared. Now I have tried everything and I think that I will have to make a claim under the warranty... Or does anyone know of a tip or similar experience...? Thank you very much.