I have been using a Sunto 9 to record my Windgoil sessions. I recently updated my The Sunto app on my phone. I would strongly recommend against it.
Here is a photo of Tracks and date pre update


And here is a photo of Tracks and data post update

I have contacted Sunto who inform me the upgrade is to give "more detail "???

Maybe the upgrade has overwritten some settings. It looks like the trackpoint recording frequency (or whatever it is called) has been increased by lot. eg it used to record trackpoints every second and now records every 60 seconds, hence the straight lines.