Foliage painted onto a landscape will disappear when Sections per Component is changed from 1x1 to 2x2.
Affects 4.17.2 CL 3658906, 4.18.2 CL 3794801, 4.19 Main
Possible Workaround is to set the Resize Mode to Resample before applying changes
Expected: Changes to Component Size applied, foliage not affected
Result: Changes to Component Size applied, foliage disappears
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-53343 in the post.