That’s CPU issues. Lunaris can be very CPU hungry, in particular, if many layers are in use, combined with multiple active reverbs and effect chains and specifically from the 05. AmbieticA category.

To reduce CPU check if more than one reverb is turned on and then turn off all reverbs, leaving only one reverb active. It’s important to turn the reverbs off, otherwise, they remain active and consume CPU.

To further reduce CPU consumption, click the Make Global button in the effect section, so all layers go through one effect chain only. This can drastically reduce CPU.

You can also increase your audio buffer size, make sure the buffer is not set to less than 10 ms (441 samples) then keep increasing the buffer until you notice a drop in CPU usage.