if the GPS glitches it''l just draw a staight line when it can't 'see', and guess.... that would be more down to connectivity than the app, per-se.
I don't use Strava, use mapmyride, but had a thing where the phone must have dropped out signal for 2 mins and decided that I'd covered that blackspot instantly, thus giving me a silly top speed and a better average speed for the ride.