No changes to the container image, but I had to fiddle with the config file. There is an option (tokenExpirationHours) to set for how long a token is valid, default is 2 hours. I can only find this in the commented example config, setting it to sometime really high like 50 let my friend upload his audiobooks without problems.

Create a config file and place it somewhere the container can access it. Then add the environment variable FILEBROWSER_CONFIG=/some/path/to/your/config.yaml.

Here is a snippet from my config:

server:
  # ...
auth:
  tokenExpirationHours: 50
  # ...
userDefaults:
  fileLoading:
    maxConcurrentUpload: 100 # The inferface only shows up to 10 so I don't know if setting this value higher does anything
    uploadChunkSizeMb: 10

tokenExpirationHours is the key to set.