Compose new email / use of old imported drafts - window size fault

Sometimes we have the problem that the new email composer didn’t recognize the window size, also the main email viewer.

So we have rarely messages with two scrollbars. That’s not really user friendly.

Below an image with the main message viewer in the background and the composer in front. I extracted all texts out of message without the long row.
If I add new text in reply to the new text will be wrap at window size.

Please send us the message that displays incorrectly to as .eml file. Thanks.