@SPaceBar I started a project from scratch, and copied the group "Phantom" from another project I also created from scratch, and then I drawed everything. After that I grouped the llama, made the symbol and used it. I did not use colour tags.
I noticed a way to reproduce the crash:
Open the project as @Komatös explained, with the layers tab hidden.
Remove the right half of the llama (it's the symbol). When I open the file it appears as selected for me, I only need to press delete to remove it.
Then drag and drop the symbol again and flip it with Transform -> Flip Horizontal.
Now if I try to open the layers the app crashes, sometimes it does not crash instantly but crashes when I select any element of the drawing.
I hope this helps, otherwise I can try to record a video.
Thanks!