Syncthing shows “Up to Date” but application file (csLaunch) stops updating over time in multi-session environment

Support
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Hi all,

I’m experiencing an issue with Syncthing in a multi-session (TSplus) environment where synchronization appears healthy, but specific application files stop updating over time. I’ve done extensive troubleshooting and would appreciate your guidance on whether this is expected behavior or if there’s something I’m missing.

Environment

  • 3 session servers:

    • tsp-session-1

    • tsp-session-2

    • tsp-session-3

  • 1 gateway server:

    • tsp-gw-1g

  • All servers run Syncthing as a Windows service (Local System account)

  • Folder shared across all nodes:

    C:\commsoft

  • Critical subfolder:

    C:\commsoft\commsoft_ini\AppData\Roaming\Commsoft\Oases

    Application Context

    We are running an application called Oases (Commsoft).

    • The file *_csLaunch.ini stores user favorites/settings

    • Each user has their own file (e.g. akacloud_csLaunch.ini)

    • These files are actively modified during application use

      Observed Issue

      • Initially, everything syncs correctly

      • After ~24–48 hours:

        • Some users report their favorites are not saving

        • Their csLaunch file stops updating locally on one server

      • Eventually:

        • The issue spreads to other session servers

      Key observations:

      • Syncthing UI shows “Up to Date” on all nodes

      • No errors or out-of-sync indicators

      • If I manually create a test file → it syncs instantly across all nodes

      • Only the application-generated files stop updating

        Important Behavior

        • If I delete a user’s csLaunch file:

          • A new file is generated when they log in

          • Sync works again temporarily

        • After some time → the same file stops updating again

          Troubleshooting Already Done

          Syncthing-related:

          • Deleted index database (index-v2) → full reindex

          • Confirmed correct Syncthing home path

          • Verified all devices connected and sharing same folder ID

          • Disabled Watch for Changes on all nodes

          • Set Rescan Interval = 30 seconds on all nodes

          • Restarted Syncthing services across all servers

          • Verified no .stignore exclusions

          • Confirmed manual file creation syncs perfectly

            File/system-related:

            • Checked permissions (full read/write/modify)

            • Verified path consistency across all servers

            • Confirmed no AppData redirection issues

            • Searched for alternate csLaunch locations (none found in use)

            • Cleaned up .sync-conflict files

            • Tested with fresh file creation (works initially)

              Key Finding

              When the issue occurs:

              The csLaunch file stops updating even locally on the server where the user is logged in

              This suggests:

              • Syncthing is not missing changes

              • The application is no longer writing to the file (or not flushing changes)

                Question

                From Syncthing’s perspective:

                • Is this expected behavior when an application:

                  • keeps files open for long periods

                  • writes in-place without triggering filesystem events

                  • or uses non-standard write methods?

                • Is there any Syncthing configuration that can better handle:

                  • frequently modified INI-style files

                  • long-lived file handles

                  • multi-session environments?

Thanks in advance for your help, happy to provide additional details if needed.