Duplicate Slack notifications

We are in the process of moving our repositories to our current github account from a previous account.

We have a Slack channel that is subscribed to both accounts.

On repositories that we’ve moved from the old github account to the new one, we are getting duplicate notifications. New repositories don’t have this issue.

I’ve tried a number of things to stop this from happening but it seems the choices on these moved repositories are duplicate notices or none. The only way to prevent it seems to be to subscribe to individual repositories. There are way too many repos to make that viable.

Has anyone seen this? Any ideas how to stop this from happening?

tia - bill