External users often stuck in lobby without being noticed. Known issue or bug?

DanHuber thanks for bringing this up for discussion. This issue is acknowledged by many tenants. https://answers.microsoft.com/en-us/msoffice/forum/all/people-stuck-in-lobby-in-ms-teams/66c24b2f-aa90-4534-84c1-9777ef4f7980 confirms 100+ other tenants and it has 3.5K views. We have so far only had this reported for about 5 external users at 5 separate occasions, but my suspicion is that it happens more often without users notifying us. Also, some participants have been highly important executives thinking we never admitted them to the meeting -- it certainly does not look professional.

Our current fix is simply telling users to activate the lobby for critical meetings, which seems to be working but is not an acceptable as we sometimes have meetings with up to 250 guests.

I have also had a ticket open with Microsoft since May, fighting hard to make them understand that it is likely to require high level engineering and tenant-level diagnostics. After almost going insane from "does your policy allow external users" type of solutions, I might finally have reach someone that is about to escalate this. He has confirmed they have multiple other open cases on this issue. He also suggested using the M365 admin centre feedback form, logging the issue with a 1 start rating as that goes directly to the engineering team. I have been asked to try reproducing the issues whilst running Fiddler on the organisers machine. But let's see how that goes, if we even can convince an external user to test this after they had the issue.

I know your issues started earlier, but for us it appeared to have started in late April. I suspect it might be connected with Microsoft's announced update of the Teams Global default meeting policy, intending to changing the default lobby from "Everyone" to "Only people in my organisation" (MC209349, now deleted...). Their message also identified the change as a https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.microsoft.com%2Fen-gb%2Fmicrosoft-365%2Froadmap%3Ffilters%3D%26filters%3D%26searchterms%3D63388&data=02%7C01%7Co365sup5%40microsoft.com%7C68e2acf5febd450a15ed08d807a7f0d6%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637267765178497161&sdata=4rgh5rVwrtBLCKi9nImEj7%2BxD890K1pZIPf7GG5ECbY%3D&reserved=0:  Today, we received a new message (MC218620), referring to the previous one, as "This feature was rolled out but due to an issue was rolled back.". Of course I cannot guarantee that it is connected, but our issues, your post and the answers.microsoft.com post, all came shortly after this change.

Hope we can see a solution to this in due time.