Many emails I work on are missing content on test send or normal send. The preview looks fine, but when the email is actually sent several random pieces of content are missing. Buttons not showing, lines of text missing, etc. I’ve spoken with support about this in twice and each time they said they too see the problem but can’t figure it out and escalate the issue but I never hear back from them. Just today I’ve been woking on a tweaking an email for over an hour to see if I can get around these issues.
I’ve seen this occur when content is copied into the email from a source like Word. This is usually caused by hidden html tagging, when content is pasted in from another source. It is recommended to take outside content and paste it into Notepad and then copy it out of Notepad and paste it into the email builder, as this will strip the formatting and hidden html. You will just need to adjust formatting in the builder itself.