I was having this happen a couple times and the liftgate only opening half way alot. Finally pestered my dealer to do this TSB. Seems to have fixed it.
TSB# SSM 49914.
Summary
Some 2015-2021 Edge, 2016-2018 MKX, 2019-2021 Nautilus, 2018-2021 Expedition/Navigator, and 2020-2021...