You may have noticed sometimes you can still hear the oscillators very faintly if there are no notes playing and you turn the volume up. This is filter bleed. Rest assured there is nothing wrong with your instrument.
Due to the analog nature of our instruments, they have about an 80 dB signal to noise ratio. If you're used to digital instruments or plug-ins with zero noise floor, this can seem abnormal to you. The good news is, it's usually only possible to hear this at very high volumes or with headphones and it can't be heard under normal playing conditions. What you're hearing is normal and shouldn't affect your mix.