Upon reloading editor some skeletal meshes, materials & textures disappear, please help

Upon reloading a project in the latest version of Unreal Engine editor 4.21.1 for Linux, some skeletal meshes, materials & textures disappear completely from the project, the references of said files are there but if you click on any of them to take a look in the editor there is literally no texture or mesh etc there, they are invisible. So for instance if you click on one of the skeletal meshes, you’ll see the details, if you look in the details, where it shows the skeletal mesh it links to the correct file, but you’ll see even in the picture preview, it is a picture of nothing(but not blank or white, just invisible). They turn completely invisible within levels as well. If I replace the files and reload the project they will appear again, only to randomly disappear again upon a project reload. The animations are blank as well, it’s like all references turn invisible but are still linked.

I’m also experiencing an issue where the palm trees from the desert rally race demo will partially become invisible within a level, until you get very close to them & I believe it is related to the other issues because after reimporting the palm tree files it is temporarily fixed. Any help would be appreciated.

I don’t notice any of these problems when running Unreal Engine 4 in Wine, however doing so causes its own problems for instance, you are not able to build lighting in Wine, and the engine will randomly freeze the entire system forcing a hard reset.

Update 1: I’ve noticed that at least the palm tree issue may be caused by enabling the apex plugin, is there a way to fix the issue? I need this plugin for my project.

Update 2: I noticed that the materials, meshes & textures are only going invisible within the editor itself, and if I launch a level through the launcher button in the editor, the things that were invisible now become visible.