I've had this problem often enough, it's not the gravity, it's the radar claiming you're on a landable spot while you aren't.
What can help anyways, but not without risk, is smacking the ship down. Not as strong to break the shields but a not so gentle impact can also make it acknowledge the position.
The risk with this being, although it happened to me in a while, is that usually when I did that I was thanked with the stuck landing bug where you can't take off.
It might that they got that bug fixed but I still play it save and unless I need to desperately land where I am do I just got for another spot.
I also hope they change the displaying of landing spots so that instead of flickering when you're over a suitable it would just blob them in a different color on the surface scan, that'd make landing in rough terrain so much easier. I'm sick of flying over places that are flat enough for my ship but won't be acknowledged because eff me -.-