So with recent issues I used Revoke All and connected all projects one again. I used this chance to separate projects better between various calendars.
Sadly after just a few hours I started to receive notifications about sync issues again, goes for 2 days now. However it applies mostly to one calendar so far, maybe is related to having "." in name? Though tasks synchronized fine right after granting access.

When clicking link I receive information in bottom toast "Calendar already exists". Can not include screenshot as I relogged today all Google accounts to change default and so it opens it on other account than where it synced it (reported issue is not related to these).
Hi, We apologize for the repeated Failed to sync notifications you're experiencing. It seems that the current Google integration may be unstable. Our team is actively investigating the issue and working to resolve it. We will update you once we have more information.
In the meantime, please refrain from reinstalling the app or you may need to reinstall again after the update. Thank you for your understanding.
Golda, Oct 8, 2024
Hi, Our team has updated the Google Calendar integration. You can now reinstall the app and check if the failed to sync notifications persist. If you have any questions, feel free to reach out. Thank you!
Golda, Oct 14, 2024