Cancelling DisplayDialog because it was run from a thread that is not the main thread: (bug)

I have had this bug that keeps randomly popping up I've searched online but haven't found a way to fix it, so thought I'd come here,

Cancelling DisplayDialog because it was run from a thread that is not the main thread: Moving file failed Moving Library/ShaderCache/vfx/BlouderStrike919c/02/aa72ad713470af61dea4fd96489bbcf6.bin to Library/ShaderCache/vfx/BlouderStrike919c/00/aa72ad713470af61dea4fd96489bbcf6.bin: The system cannot find
the file specified.

This is the full text, it seems to happen when I use a SECOND output particle mesh inside a single VFX Graph, if I ignore this the compiling gets slower and slower sometimes up to 1-2 minutes, I've attached an image of the emitters they're very simple, but I've been asked to have the rocks spawn separate due to a script the dev's are looking to implement, this bug however did occur on a previous effect I was working on and ended up splitting the vfx graph in two separate parts, but I don't like the idea of having 16 separate vfx graphs for a single mesh.

 

Hi Paul my apologies, I should've added the version I'm using, I'm using 2021.2.8f1 this is the version our studio is using. I did see the issue tracker so assumed there might be a way to fix it.