Ok so it seems this modulation is too much to handle for the DN. The CPU is a bit underpowered on the DN and I recalled Ess saying there are some safeguards like first it is the UI that will be slow before it is the audio. For instance the LP4 filter is always decreasing UI response time while using Over bridge.
Maybe you could try a workaround by modulating the modwheel or breath controller on which you affect the volume and check if it still happens. And you could also try decreasing the resolution of your LFO, so it have less values to send.