This is an issue with Marketo Editable sections of the email's code. There seems to be a default setting to automatically change "&" to "&", and it is also tampering with GA tracking.
"<td class="btn" style="font: bold 11px/15px Helvetica, Arial, sans-serif; color: #0c8eda; mso-padding-alt: 13px 20px 12px; border: 1px solid #2f75bb; letter-spacing: 1px; border-radius: 2px;" align="center" bgcolor="#FFFFFF"><a href="https://www.WEBSITE.com/aboutus/?utm_campaign=platform&utm_source=newsletter&utm_medium=email&utm_term=platformupdate&utm_content=cta" target="_blank" style="text-decoration: none; color: #0c8eda; display: block; padding: 13px 20px 12px;">CTA LINK</a></td>"
This is not occurring to utm links outside of Marketo editable sections. So I'm not sure if I should just stop making those sections editable anymore.
Does anyone know how to stop Marketo from changing the "&" in UTM links by default?