Can you please post some screenshots of what the button looks like in the Marketo editor? and when you actually receive the email?
If you are saying that the test samples are working fine, then I find it hard to believe that having the email as dynamic is making the button spit out html code for that variation, unless it has been modified for that specific variation.
But some examples would be good so it can be trouble shooted.
Also regarding with viewing in browser, can you confirm that you are seeing this issue with the actual email and not a "test-sample" email?