I am using Syncthing-Fork on Android, but the issue seems to be in the backend, as it is visible in the Weg GUI, too. The Global State is widely out of sync, and files are only synced to the mobile when they are changed anywhere else, which is quite annoying. The issue is only on that device.
See also Only syncs updated files · Issue #894 · Catfriend1/syncthing-android · GitHub
Might be related to Not syncing properly, database error Can I pass a flag to the syncthing instance running in the background of the app on a rooted Lineage?