Spiky extra lines (Forerunner 645)

I have been using basic Forerunner 645 for some time. On yesterday's walk, for the first time ever, the plot of my walk had a series of extra lines spiking back and forward. I checked by looking at the individual kms. All the spiky lines, which looked like several extra kms were in fact all in one km in the middle of my walk, at a point which I have visited many times in the past.. Presumably this was due to a loss of signal. I was not aware of any unusual action on my part, nor any warning from the watch, Does anyone have an answer as to what may have caused it. Also advice on how to avoid it in future. Also advice about removing the extra lines from the plotted trace (not essential, as no distance seems to have been added).

 

Thanks Nuvi-Nebie. No pause involved this time though.
I went up a road, turned and went back down. Reasonably open area, suburban housing estate, with houses set back from road and no large trees or other obstructions to interrupt line-of-site satellite cover.
Regarding the distance: What I meant was that the length of the traces on the plot would have amounted to several km. The fact that all these lines were within one highlighted km suggests that the plot did not result in any appreciable distance being added to the total.