Tbh I can't remember anymore...
Maybe have a look in here, according to my post the solution should be there
Maybe my config helps too.
I have no idea if it's "technically" correct, but it's working.
Docker Syncthing Config:
Network Type: Bridge
Console Shell command: shell
privileged: off
Host Path2: /mnt/user/AndroidBackup --> AndroidBackup is my created share.
AppData Config Path: /mnt/user/appdata/syncthing
Syncthing Webui:
Folderpath: /sync/FullBackup --> "FullBackup" is the folder inside your created share where the actual files are stored
No real solution to your question, but I hope I can help anyway.