Background Callback and Regular Callback do not share same data?

Hello, I have a question about background callbacks using Celery and Redis.
I have configured my app to run some background callbacks, as it would help with potentially larger callbacks that would timeout otherwise.
However, I have run into a very specific issue that I am unsure of and would like some clarification about.

In a previous callback, that is not a background callback, I have the user upload data using dash-uploader to a certain directory. When using glob in that callback, I get the following filelist:

[.profile.d, .release, .heroku, __pycache__, components, 
.config, .cache, upload, .env, DOKKU_SCALE, Procfile,,, apt-env,, colors.txt, requirements.txt, runtime.txt, setup.R]

However, when I use glob on a separate callback, this time the one which is a background callback, it doesn’t show the upload directory.

Is this because background callbacks share a different file storage system as non-background callbacks? Is there a way for the background callback to access these files?

Thank you!