Area Class and Is Dynamic Obstacle properties do not seem to be saved on static meshes under certain conditions.
I was able to reproduce this issue 3/5 times that I tested it. It seems that if the assets are opened one at a time and the changes are made to each individual instance. It also seems to matter if the assets are saved individually or as a group. When I used Save All, on multiple static meshes, this seemed to trigger the property-saving issue.
Result: It's inconsistent which of the properties will be reset, but either the Area Class, Is Dynamic Obstacle, or both will be set to the original value that was stored before modifying it.
Expected: The changes made to the properties would be kept.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-44583 in the post.