proxmox cluster igmp with HPE V1910-24G Switch

das hat letztlich geholfen:

Linux: Disabling Multicast snooping on bridges

Snooping should be enabled on either the router / switch or on the linux bridge, but it may not work if enabled on both. If you have a hosting provider that has igmp snooping enabled on the multicast switch, it may be necessary to disable snooping on the linux bridge. In that case use:
post-up ( echo 1 > /sys/devices/virtual/net/$IFACE/bridge/multicast_querier )
post-up ( echo 0 > /sys/class/net/$IFACE/bridge/multicast_snooping )