Issue with dynamic QR codes for events

Hi all I'm trying to create QR codes for live events so we can scan people in to capture attendance.

I am using this code to insert the QR code unique to a person that wen scanned triggers a blind form submit to capture the attendance.

<img src="https://chart.googleapis.com/chart?chs=300x300&cht=qr&chl=https://app.response.auckland.ac.nz/e/f2.aspx?elqFormName=EVENTQR&elqSiteID=XXXXXXX&emailAddress=~~eloqua..type--emailfield..syntax--EmailAddress..innerText--EmailAddress..encodeFor--url~~&EventAttendance=Attended">

when the email is delivered there appears to be a QR code as expected but when I decode it looks like maybe the link is too large as it translates to only a portion of the URL

has anyone else experienced this, have another way to capture live event attendance or perhaps have an idea to get around this issue?