Unable to access sites w/ VPN which require a login or can't post

I've just updated the OpenWRT install on my router (a WRT32X) to the following ...

openwrt-19.07 branch (git-20.341.57626-51f55b5) / OpenWrt 19.07.5 r11257-5090152ae3

Also, I use an OpenVPN client setup with my VPN service being PrivateInternetAccess. I've always been able to access these sites by logging in before.

I can now browse sites fine (so I believe my DNS is working fine), but the issue I'm having is that I can't login to sites like gitlab.com or gmail.com. Other sites like this one (openwrt.org) I can login, but I can't post unless I turn the VPN off. I'm always getting http 408 errors.

Any thoughts as to what might be going on here?