@KhaineGB Cheers on the alpha 21 test mate!
I've been smashing different plays lately and trying to look for any additional bugs, I'm not sure if it has been brought up yet, but for the older alpha POIs specifically "The Grumpy Residence", the mission activation is in the ground and if you dig to it, the marker doesn't appear. I have yet to find this on any of the present POIs as of yet but this is also the only older POI I have found to have the issue so far. I'll update you if there are any more to be found that you might not be aware of.
https://imgur.com/xOF8E77
https://imgur.com/aJJad5Y
FYI apologies for the links to the images, the insert isn't working for some reason.