The scene file just has one person, Wendy, in it. Although the timeline plugin isn't on her after loading the scene, but in the json file, so any way there are some problems. I get a lot error messages about missing content of course, morphs, textures etc. - don't know if that could interfere with scene loading.
If you have been working 1-2 years on that scene, do you only have that one single file you always overwrite? I guess you already know that you should always make backups and save different versions. You can use a plugin for that to do it automatically in the future:
https://hub.virtamate.com/resources/autosave.23320/
Though i hope you can restore the scene or have some older files for it. I have overwritten and lost hours of work in my beginning days, data loss hurts :/ Good luck to you.