I can ping through VPN-tunnel but not browse host

[Ritte]

Hello! I've set up a site-to-site vpn (OpenVPN) using two pfsense-routers. I've set the firewall rules and everything seemed to work perfectly until I found out something strange.

This is my network:
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The issue that I have is using computer B (192.168.1.10) I can always ping pfSense on site A (192.168.4.1), but sometimes it takes a while before I get into the login-page. When the issues occurs (it doesn't always!) it's either very slow to browse site A or it times out. I've tried with SSH, it's the same thing. Keep in mind that while this occurs, I can always ping pfSense (192.168.4.1) and Computer A (192.168.1.1), but it's browsing that seems to cause the problem. When site A is slow it's all hosts on site A that is unbrowsable.

I also have a "road warrior"-VPN that I use for my iPhone, it uses another vpn-tunnel rather then site-to-site VPN. The problem doesn't seem to occur using the "road warrior"-VPN.

I've setup computer B to ping computer A every minute, to capture if the ping fails and it seems that I can always ping site A from site B.
I've ruled out that it's firewall rules since I sometimes can browse site A with no problems.
I've also ruled out (I think) that it's a routing problem since when I try to browse pfSense A (192.168.4.1) and Computer B (192.168.4.10) it get's logged (as passed) in the firewall logs in both pfSense on site A and Site B. That concludes that the request goes trough the tunnel.

My theory is that there may be some kind of packet loss, which causes this, but I don't know how to debug the tunnel. Maybe you have any idea of what the problem may be?

Thanks!

[gcu_greyarea]

I would start by checking MTU sizes with the ping command.
Why not use IPSEC for your site-to-site tunnel ?