OK.
To configure the IGMP version on a switch:
[edit protocols]
user@switch# set igmp-snooping vlan vlan-nameversionnumber
"Note: Configuring the IGMP version does not limit the version of IGMP messages that the switch can snoop. A switch can snoop both IGMPv1, IGMPv2,, and IGMPv3 messages regardless of the IGMP version configured."
https://kb.juniper.net/InfoCenter/index?page=content&id=JSA10714&actp=search
PROBLEM: