Maximum size of a single map is 20km, physics start having problems after ~6km. So yes, at 50km things are going to get weird.
There’s been plenty of topics about how to get past those limitations, the best particular approach is going vary a lot depending on your game. Although not Unreal Engine, the Kerbal Space Program team has discussed addressing similar issues in Unity Unite 2013 - Building a new universe in Kerbal Space Program - YouTube