Hi Tom, technically, this problem is not a bug in the MainWP system.
I will try to explain.
When you connect your child site to your MainWP Dashboard, it creates OpenSSL encrypted connection where the pubkey is saved on your child site (in the database).
When you push changes from the Live Site to Staging, it includes the pubkey value and since the pubkey is set, the system thinks that the connection is already established. When you deactivate/reactivate the child plugin, it clears the pubkey and you can reconnect it again.
Only way to fix this is to check with Gridpane support if there is a way to exclude certain wp_options fields from being pushed from life to staging sites, if yes, have them exclude the
mainwp_child_pubkey field and that should solve the problem.