LDAP Connection Error - io_fillbuf

I’ve configured LDAP, I believe properly, but each time I try to connect, or run

gitlab-rake gitlab:ldap:check

I get

Net::LDAP::Error: Connection reset by peer @ io_fillbuf - fd:9

I found one forum post from a few years ago on this suggesting it’s because we use an enterprise internal CA, but I’ve added the root and intermediate CA to the server’s cert store and they now verify without issue. Any thoughts?