I’ve noticed this problem with Mission Planner since 1.3.51. In Plane mode it gets the elevation graph wrong. In the screen shots below from 1.3.50 and 1.3 53 the same mission is loaded. Its a terrain follow height of 60m above ground in a simple square.
In 1.3.50 it charts it perfectly a constant 60m above the ground. In 1.3.53 it shows a sudden climb, drop then climb in altitude (circled yellow). On some missions in 1.3.53 it shows this drop below ground level.
Also, in 1.3.53 it’s not showing the green Google info line in the graph.
Version 1.3.50 - Correct
Version 1.3.53 - Graph wrong