Read receipts aren't updating in group DMs

[MrConorAE]

I installed the bridge yesterday and just noticed that the "seen by" data is inconsistent with Instagram's own app, often showing users as having not seen the message when the Instagram app says they have.
For example, I sent a message using the bridge, and Element shows that no users have seen it (it's just the checkmark circle, and all the mini profile photos are further up in the timeline) - but in the Instagram app, it says that users have seen the message.

Not sure if this is an issue with my install or the bridge, and if I'm honest I'm not sure how to check. I installed it using the instructions at https://github.com/beeper/self-host/blob/main/README.md on a VPS. If you need any more info, let me know :)