The issue appears to be some asymmetrical routing to the pool addresses you have setup on the SSL VPN. Adding the route to the server prevents the asymmetry with the firewall hop.
Options would be
Change the pool to be in the same address range as the SSL interface. I assume this is setup single arm on one interface.
Change to dual arm with the second interface on the SSL having your pool subnet and a gateway to your firewall on its own. Then your sessions will be from this zone/interface and fully symmetrical to all devices.