haven’t tried it myself but they added a feature just for this purpose.
select your landscape and in the Details Panel look for “Bake Material Position Offset Into Collision”
glad you found a fix for the issue, but adding a bigger bounds would [on the paper] just cause more rendering overhead (some components will be rendered even if they are out of the view) though it might be negligible due to the fact that it’s only a Z bounds extension.
I’m curious if this other method would fix the original issue: go to the landscape tools, find the one called “Change Component Size” and just hit Apply. this will in theory re-create the landscape so the collision should get a fix if anything is wrong
using “Bake Material Position Offset Into Collision” might just fix the original issue too