@seoergoweb thank you for confirming once more. Our engineering team has investigated and provided their findings via the GitHub issue.
We have explored the possibility of SALT keys changing and don’t believe in this case this would be causing the issue you are having.
This leads us to believe that in this case the the 50 refresh token limit is being hit which is creating a new refresh token automatically invalidates the oldest refresh token without warning.
We can see that you have close to the oAuth refresh token limit of 50 and even though that isn’t quite at the limit with Site Kit sites, it’s possible that you may have other oAuth connections set up that could be adding towards a refresh token limit. Site Kit holds on the refresh token to stay connected to the oAuth service, if you hit the refresh token limit, your oldest refresh token will be invalidated resulting in you needing need to re-authenticate to get access to the API data.
This limit is something that is being looked into by the team but for now our recommendation would be to limit the number of sites connected for each account to around 20 (or maybe 30), creating new accounts as needed to manage additional connected sites. That will likely stop the disconnects.
Please do let me know if any of this doesn’t make sense and thanks for your patience throughout.