Continuous Ping not sent to VPN

Hi!

I have a strange issue:

Host pings another host through the VPN. If the "other host" is not reachable, there is only sent ONE of the pings to the VPN-tunnel.

I am running:

diagnose sniffer packet VPN-Tunnel

and I see only the first of four echo-request.

If I wait for about 60s and restart the ping, I see ONE more packet.

Is there something like a cache?

I already set "auto-asic-offload disable" on the firewall-rule.

How can I change this behaviour?

Thank you and best wishes

KPS