Home Point Confusion

I’m having some difficulty wrapping my head around setting a Home point with the latest version of Missionplanner and Plane 3.9.8.

Doing anything from the “Flight Plan” screen has no effect on home point. Things I’ve tried:
Right Click -> Set home here
Clicking and Dragging the point
Clicking “Home Location” to set it at the plane’s current location
And, after each of them, clicking “Write WPs” to send it to the plane.
In each case, after reading back the waypoints, it asks me if I want to reset home to loaded coordinates. I presume this means “the coordinates loaded to the plane” so I click Yes, and it moves my home point back to it’s original spot (wherever I powered the plane on) every time.

There is also the option of doing it from the Flight Data screen.
Right click -> Set Home Here -> Set Home Here
Using this option DOES move the home point that gets recalled when I read waypoints, to wherever I placed it. However, it messes up the altitude. My plane goes from saying ~0ft altitude, to reading anywhere from -50ft to -120ft AGL altitude on the HUD, the moment I click Set Home Here.
I am aware of the Set Home Alt button in the Actions tab, which, If I am understanding it’s function correctly, should reset that displayed altitude back to 0. However, it does not appear to be working correctly, as it simply toggles the displayed altitude between two incorrect values. In my most recent test, it was ~-20 and ~-70. No matter how many times I clicked it, I could not get a 0 altitude reading with the plane on the ground, like I had before setting home point.
It is worth noting that, even if the “Set Home Alt” button were working correctly, I wouldn’t be able to use this feature in the air because that button is only meant to work on the ground. I would need the “Set Home Here” option to not change the altitude in the first place.

Currently, the way I am getting around this is to rely on the aircraft to reset it’s own home point while it is disarmed. This works in situations where you know for a fact that the takeoff location will be safe to use in event of RTL, but in a real-world commercial application such as surveying or inspections, this simply will not always be the case. If the environment changes so that I can no longer land at the takeoff point, and a Failsafe/RTL situation occurs, I need to be able to change the home point quickly and accurately to avoid incident. In addition, simply being able to set a home point as part of the mission plan would be handy, if you wanted to use a home point different from your takeoff point in the first place.

Are there any tips or tricks that I’m missing?

The waypoint 0 on mission list is the home point !

Are you saying that the home point is sent along with the mission file whenever you click “Write WP”? That doesn’t seem to be working in my case, unless I have something configured wrongly.

I’m using Copter, but if I need to divert using the GCS I use guided mode to move to a safe location and then the land command. Rather than resetting the home point could you use guided mode to land in a different location in the event of an RC failsafe?

Or Rally points.
Rally points dont change unless you delete and upload new ones, so check all related settings or your craft can head off on a 64km journey to some old rally point.