Qsync Client for Mac 5.1.7: Finder extension terminates itself (terminate: called on background thread)

English General
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ENVIRONMENT

  • Mac mini, Apple M1, macOS 26.6.2
  • Qsync Client 5.1.7.0923 (main app x86_64 via Rosetta 2; FinderSync.appex universal)
  • NAS: QTS 5.2.10 (build 20260731), Qsync Central 5.0.0.7
  • Other Finder Sync extensions: Google Drive and OneDrive disabled (both use File Provider), Hazel disabled, DAEMON Tools enabled

PROBLEM
The Qsync Finder Integration (com.qnap.qsync.findersync) stops working at random: sync badges and the Qsync context menu disappear from Finder. The Qsync Client app keeps running, and the extension still shows as enabled in System Settings. Disabling and re-enabling it under Login Items & Extensions restores it until the next time. This has happened repeatedly, also before version 5.1.7.

EVIDENCE (unified log)
The extension quits by itself. It is not a crash (no crash report), and it is not killed by macOS:

13:27:36.102 FinderSync: terminate: called on background thread. Redirecting to main thread as a courtesy.
13:27:36.103 FinderSync: replyToApplicationShouldTerminate:YES / App termination approved
13:27:36.108 FinderSync: Termination complete. Exiting without sudden termination.
13:27:36.115 Finder: Connection to plugin interrupted while in use.
13:27:36.117 Finder: extension connection was interrupted! plugin_identifier: com.qnap.qsync.findersync
13:27:36.121 Finder: tearing down extension request … {id = com.qnap.qsync.findersync}

The Mac was awake and in normal use (no login, sleep or wake at the time). Finder does not restart the extension afterwards.

At login on 2026-09-28 17:42 the same happened: the extension started at 17:42:03, was interrupted at 17:42:04 and 17:42:06, and was gone from Finder’s extension set by 17:42:16.

ADDITIONAL OBSERVATION
Qsync Client opens a new TLS connection to the NAS about every 5 seconds. This may be normal; mentioned in case it is related.

QUESTIONS

  1. Under what conditions does the Finder extension call terminate:? Is this intended?
  2. Is this fixed in Qsync for Mac 6.0 (Universal Binary)? When is 6.0 final planned?
  3. Can you recommend a workaround until then?

Full logs can be provided on request.