Bot Image Attachment Does Not Display on MacOS.

We are developing a bot which renders and sends png images back to the user. On mobile and Windows builds of Teams, we are able to display the image within an Attachment using either a remote url or the base64 png data. However, on MacOS builds, the chat displays a narrow vertical box without the image rendered in it. Selecting a reaction, thus making the attachment wider, displays a very small render of the image without any click functionality.

I should note that this issue only appears to effect individual chats with the bot; it works as expected in if used in a channel.

Additionally, this issue came up only within the past week and appears to be unrelated to any changes in our code during that time. 

This is Teams release 1.4.00.22368 on MacOS 11.5.1

var imageAttachment = new Attachment
            {
                ContentType = "image/png",
                Name = "Chart",
                ContentUrl = pngUrl,
                Content = new FileDownloadInfo(pngUrl)
            };