Hi,
the open rates just seem to increase, because the open pixel gets loaded, but your click-to-open rate decreases dramatically -> The content and subject lines get jugded wrong, because it seems that so many people are openig your mail, but don't click it . I always recommend to test new subject line concepts on recepients who never opened an email. Your subject line is really good and should be used for your active segments, if it convinces the inactive recepients to interact with your content. The same logic applies to CTAs.
Best regards
Niels