I really appreciate your feedback but I am sorry to hear you are experiencing these issues. It's definitely not what we want.
Is there any chance you have tried using Constant Contact in another browser? I would just be curious to see if the issue stems from something affecting your current browser and if it will replicate in a different one. It's possible an extension or plugin is interfering with the site experience. You could also try using Constant Contact in Incognito/Safe Mode with your preferred browser and see if that helps.
And I do apologize for any inconvenience or confusion created by having two editors. Right now you still have access to the second-generation templates when you create copies of your older templates but any fresh templates created will appear in the third-generation editor. I would check out our Knowledge Base article on moving from the second-generation editor to the third-generation editor. It might help with clearing up any confusion between the two.