Using console command 'RecreateLandscapeCollision' resets collision in areas that landscape hole materials have been placed.
Workaround: paint new hole material to re-remove collision from areas where landscape holes exist.
1. Open Editor (any project)
2. Create new landscape
3. Create new material
4. In new material, add landscapevisibilitymask, plug output into opacity input.
5. Select material node, set blend mode to "masked"
6. Save and close material
7. Select landscape
8. Set material and hole material in details pane to new landscape material
9. In landscape sculpt mode, select visibilty, LMB to paint hole in landscape large enough to show collision change.
10 press ~, type recreatelandscapecollision and press enter
11. PIE, walk over hole.
Head over to the existing Questions & Answers thread and let us know what's up.