Engine is dropping thumbnails

I’m using TrueSKY plugin with the engine and it’s changed the preview skybox too but when I open them they render just fine.
Maybe it’s a RAM related issue becauese sometimes Windows closes the engine because of high memory usage.
System specs: I7-5820K Gtx980Ti 16GB-RAM

The only thumbnail related issues we are currently aware off that are similar to this is this issue here: Unreal Engine Issues and Bug Tracker (UE-42376)

Are you getting this issue only in projects using the TrueSKY plugin? If that is the case unfortunately we can’t really account for user created content. I would recommend contacting the plugin developer about this issue.