Pubsub published messages not appearing consistently

I am working on code where we have a graphql subscription setup and an elm page subscribing to that subscription. When developing locally, messages published to that socket get delivered to the browser and I see that browser react.

When I test on staging, where potentially other developers are also active on that page subscribed to the same topic, it looks like I am not always receiving the socket messages that I would expect. My current wild speculation is that the pubsub is delivering to only one of the browsers instead of all subscribed browsers. I am considering trying to prove this by having multiple people leave the page open and seeing if all browsers get the expected message…if anybody has any experience with troubleshooting this, I am curious to hear what they have done