New user here learning as much as I can. After updating to 5.3.1 my current 5.3 project terrain has grown huge spikes, and my river spline has also disappeared.
I’m pretty new to UE so maybe there’s a quick fix or explanation that’s clear to a lot of others, sorry if I’m staring at the problem!
-Peter
Hello Peter,
I sometimes have this problem, but for me it began appearing on 5.2.
Have you tried using the landscape sculpting tool? It appears to reset it to before these spikes, that’s a strange fix I know.
But it worked for me !
Charles-
Hi,
Yes I used the landscape tool to create the sculpted landscape I have now, I did try to use the smooth tool but it didn’t do anything, maybe I’ll try a bit more deformation and see what that does, thanks. I’m hesitant to do too much without asking first because usually I mess it up even worse if I get into the weeds with no advice 
Thanks
-Peter