Calculating a geotrace from 2 geopoint repeat records

[Adrian_S]

I need to display on a map on a form a line connecting a series of geopoints.  Can anyone suggest please a better way to do it than outlined below?

The geopoints are entered by people surveying lengths of hedge to mark changes such as different characteristics or direction.

I've almost got a solution, in Survey123 (XLSForm is attached below). However, in the field app the map displays without the blue geotrace line showing: 

It's only after the surveyor goes back one repeat and manually taps the map refresh button (circled in red above) that the line appears:

Is there a way to auto-refresh, or another method altogether?

[DianaTorres10]

Yeah, I'm only using one geopoint question, that's why I'm using sum() to trace de line.