Character can't move properly on landscape

Hi guys, new to Unreal and have run into an issue when testing a map. I’ve placed a landscape down and sculpted it to my liking from a blank project. Copied and pasted my assets in from another level and tried to test the game.

The character can’t move forward in certain areas, is sped up in others, and slides off the floor or flies up in some places. I’ve just imported a clean third-person bp and haven’t made any changes to it and I’m facing this issue.

If anyone can help with this I’d really appreciate it as I’ve been struggling with this issue for days.