Terrain morphing has been an issue for a long time. There are many topics about it, some of which are logged as bugs, but of course they never really get fixed.
Brief description of the issue:
Doing flights over mountainous terrain, eg. between Innsbruck and Zurich, the mountains are continually popping and changing shape - others have described it as “morphing”. This came into existance after the USA update and has persisted through the UK and now the Nordics update, with the Nordics being the most noticeable and worst. This effect is very off putting as even if you try to ignore it, your eye is drawn to each mountain as it pops into a different shape…