Reasons for Dropped Samples other than Underrun

Hey all,

I’m doing a project with GNURadio and a LimeSDR-USB on Ubuntu 16. The model’s built, and its just a transmitter, but when I try to play the model into a spectrum analyzer, the resulting wave sort of bounces in and out of shape. Typically this kind of thing happens when GNURadio underruns, but then what I noticed was two things. Firstly, the CPU usage reported by top is not exactly capping out, which should mean samples are being produced fast enough. The second thing is that for the same model, with nothing changing except for the designated sink, a USRP does not have this issue of the bouncing waveform, but the CPU usage is much higher, though also not peaking the CPU.

I could be looking at this issue from an awkward, or bad angle, so any sort of insight or guidance would be much appreciated.