Unfortunately, without used proxy objects, the Forest object can't be rebuild "completely" to do more testing with it. I've noticed, there are two Forest objects in your scene using the same settings ("Forest010") which might be causing these troubles and I would suggest you to remove one of those. Attaching screen-shot.
If the issue persist, would you mind to send us an archive including these proxy objects? Thanks in advance. Merry Christmas & a Happy New Year.