James, I tried in both a blank T3B3 template and in j3.3's default template and couldn't produce the issue.
I did notice this css comes into play when the button briefly switches while it's working:
body div#fd.es .btn-loading {
position: relative;
padding-left: 26px;
text-indent: -9999px;
min-width: 26px;
}
body div#fd.es .btn-loading:before {
position: absolute;
margin-top: 3px;
left: 6px;
content: '';
display: block;
width: 16px;
height: 11px;
background: url('../../../../../media/com_easysocial/images/loading.gif') no-repeat;
}
body div#fd.es .btn-loading.with-text {
text-indent: 0;
}
Not sure it helps, but the above css is in
/public/components/com_easysocial/themes/wireframe/styles/component.css