Openfire hazelcast clustering session problem

I have this example setup of 3 openfire servers with hazelcast plugin installed, and connected to the same external database. HAProxy is my loadbalancer, and I use LDAP for authentication.

Everything works fine, I mean users distributed to servers according to load balancing alghorithm as expected. Problem is when one openfire server is down, not only sessions on that server die but also sessions on the healty openfire servers die too. It takes some time to reconnect.

So my question is, is there possibly any way to prevent that? I need the sessions on healty servers to stay still. Any suggestions?

Thanks in advance