Why does it look like data is missing when I use the "Shift" function in arithmetic?

The "Shift" function allows waveform data to be moved backward or forward in time. The beginning or end of a block will have the amount of shifted data "missing" and flat-lined simply because there was no data recorded during this timeframe. The duration of the recording is the same, but has been shifted the given amount of seconds out of the visible window. 
Best practice is to use the data in between the shifted areas for analysis.