Jordan,
No, I hadn't tried logging in. Wasn't sure that was a requirement to make the problem happen.
I just tried again in both Chrome and Safari. In Safari, I couldn't recreate the problem on your site or on our demo site. I tested repeatedly.
In Chrome, however, I could see the issue on your site and on our demo site. Our demo site URL that was failing was a
www.facebook.com URL and your site had the m.facebook.com like you mentioned. Doing a search, I could find a bug report in Facebook that describes the mobile Chrome issue pretty clearly:
developers.facebook.com/bugs/134865033332978
The problem there notes the URL I see on the demo site, but the I'm pretty confident the issues would be related.
I'd highly recommend using the "Does this repro describ your issue?" link in that bug report to increase it's priority.
I'm still unsure what/why you're seeing issues in mobile Safari, as we can't recreate those. Hopefully, the Chrome issues will be fixed soon though.
Alex