The first is graphics. If you have a lot going on in the plan view, or the files are extremely large, this can take some time for updating the screen and therefore give the appearance of "pausing".
The next item is the cut/fill color map? For extremely dense grids (see our demo project), the amount of data drawn to the screen takes about 4 seconds to complete based on the zoom level.
The last item is the "Update/Write Existing Grid". When any form of I/O is done to the disk, Carlson Grade will be pre-empted or pushed aside to allow the computer to do its job.
The data flow, from the GPS to the rest of the system is still moving. There should be no latency problems. Just use common sense when using an existing grid!