I was participating in a very long conversation on another forum about AirMail and Thunderbird incompatibility. The conclusion is that there is not really a fixed standard, or not one that is adhered to, for how email clients assemble the html, and so it makes it difficult for developers to provide a solution that covers all possibilities.
I find in general that eM Client does a better job, but obviously not in your case.
Can you send me one of these emails so I can see how it appears? Right-click on the email and choose Forward as attachment to [email protected]