IGMP is used to reduce bandwidth on the network. Instead of sending 1 data package to 1 client, it sends 1 data package to multiple clients. However it only works if every node in the network has IGMP. IGMP is a fire and forget protocol, so there is no control if a client received the package. Since you’re mentioning drop-outs/stuttering, it could be the case here.
A lot of network gear have this option default enabled, hence my question.
a 2nd suggestion is to use a tool like Acrylic Wi-Fi Home (There is a free version). To see if one of your neighbors is interfering with your network, using the same channel.
If I would setup my network on channel 11, i sure would have issues like you’re mentioning.
Every color is a different access point.