Packet Filtering for block ICMP Traffic

In my network design, it consists of 3 network segment which is VLAN_Internal, VLAN_ISP1, VLAN_ISP2.

So i created 2 packet filter rules to block the ICMP from external network (VLAN_ISP1 & VLAN_ISP2) and it works perfectly.

However, when i ping from the internal segment (VLAN_Internal), i found that the ping packets is intermittent drops, but when i "disable" the packet filters features on F5, and the ping become smooth..

Any idea wat will causes this problem?

thanks..

Best Regards,

Ray