Bug: Supewave detune drift?

I found this odd bug (?), which is typically not a problem but could be annoying. After fresh boot everything is fine and all the waveshapes in DDS1 are nice. But, once Superwave is activated and detune is raised, it will leave some small residue which distorts DDS1 waveforms even when SW is turned off. This is very visible (and audible) with SAW for instance. And, it will vanish only after reboot. Just try to raise Detune, then lower it back, and see that the voice still hase some small amount of distortion. By switching SW to 1/2 and lowering detune it can be fixed but for each of the 6 (12) notes it has to be done manually. I guess there is some bug in the FPGA? (see scope image)