I am facing same issue but this solution didn’t resolve my issue.
I’m using custom login field “sky”.
I’m redirecting URL of my old website (.aspx pages) to new website (WordPress) and getting this error only for such .aspx pages.
Any clue?
Disabling ‘APC Object Cache’ worked, didn’t get that fatal error again. Website is bit slow to load but it is worth instead of showing fatal error.
Thanks @jkhongusc and you win the bet… 😉
@jkhongusc, If I flush server cache, that fatal error goes and website came back to work. So I disabled ‘APC Object Cache’ plugin to start testing. I’ll keep my eye on the website for fatal error and I will update you for the outcome. Hope this will work.