GPS stops recording distance but time continues AND the map shows whole route. What’s wrong?

Done 3 runs with new FR 745.

run 1 looks ok

run 2 shows last km split as 24mins! Post run map has the route. Total time is show (timer kept going)

run 3 pauses at 5.56 km for many minutes and then restarts keeping pace. Map shows full route; timer shows full time

what do I need to do to fix?