CSS formatting of M2 login form error message in PopUp Pro modal

I'm using PopPp Pro on a CSS trigger to create a login popup on my site. I'm having a little trouble with the display when a user puts in the wrong username/password (for login) or the wrong email address (for password reset). The error message gets written over the top of the login or password form, so it becomes unreadable and unusable.

It works alright if I make the popup wider -- then the login form (which is coming from the Membership2 shortcode [ms-membership-login]) is positioned to the left, and the error message appears on the right. But before the error is triggered, it's awkward looking with a big blank space to the right.

I'm hoping there's a way to make the error message appear above the form instead of on top of it. Been knocking my head against this for hours. Hoping someone can suggest a solution.

The problem can be seen at http://mclone.nrocnetwork.org - just click on the "Account" link in the upper right corner and try to login and/or reset password. Since your information won't be in there, you should see the error without much effort.