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#1421 GCSM resyncs the same contacts from Google to Outlook, Calendar syncing not working.
I installed the latest 4.3.0 and GCSM syncs the same contacts from Google to Outlook over and over. It never sees those same contacts on Outlook as being current. In addition, it is not syncing new calendar items FROM Outlook to Google. In other words, the program is simply not working correnctly at all right now. I also tried updating .NET to the latest version of 8 and that did not have any effect.
GCSM Version 4.3.0
Microsoft® Outlook® 2021 MSO (Version 2601 Build 16.0.19628.20166) 64-bit
Windows 11 Pro 25H2
And I just tried 4.1.34 and it does the same thing.
And tried 4.2.1. It doesn't try to sync all the contacts every time but it won't sync Outlook Calendar with Google.
Roll back to 4.1.33. Its the last version that works correctly. I have seen many bug reports of people saying the same thing and as far as I know, it has not been acknowledged by the devs. Hopefully at some point a fix will be released so we can all update past that version.
I've tried going with that version too and it doesn't work either. It has a tendency to duplicate contacts as well. I have switched to MyPhoneExplorer for now because it works. It's not as nice as a fully background process since it requires its own Android client but I have not seen any issues with the calendar, contacts or tasks. I donated to the dev here a long time ago and I'd donate again if the project had any signs of life. Sadly, it seems abandoned.
I’m maintaining an unofficial fork of GO Contact Sync Mod because the upstream project appears inactive.
Part of this report sounds similar to an issue I worked on in my fork: repeated re-syncing of unchanged contacts. My fixes are strongest around contact sync behavior, deletion-prompt behavior, profile/folder persistence, and Outlook startup handling. I would not assume this fixes the calendar side of your report, but it may help with the repeated contact resync behavior.
Current jkfix release:
https://github.com/jaywking/go-contact-sync-mod-jkfix/releases
Source and issue tracker:
https://github.com/jaywking/go-contact-sync-mod-jkfix
It’s an unofficial fork, so please back up first and test carefully. If you try it, I’d be interested to hear whether the repeated contact resync issue improves.
Same issues as Tom above. I'm running 4.3.0. Any updates from the developers?
Last edit: David Benson 2026-04-20
I have to stop using this until it is fixed. Too many headaches. Any reliable alternatives for Outlook/Google contacts and calendars?
Hey. Give this a try, if you'd like:
https://github.com/jaywking/go-contact-sync-mod-jkfix
For the calendar sync, I use: https://www.outlookgooglecalendarsync.com/