Subscribe by email plugin: Newsletters sending multiple featured images

I love the subscribe by email plugin and we use this weekly for all of our 25k+ subscribers. However there are issues with the formatting of the emails that go out. It shows only one featured image in the test emails but when we send the emails it comes up with two featured images, one of the image and one blank. Is there anyone who has found this and fixed this? I have added a screenshot to show.

Its frustrating and I would love to continue using but I cant find a way to remedy unless I remove the featured image completely which is not as impacting for the users.