Azure SignalR frequently not receiving messages

Question

We're having some issues where the Azure hosted SignalR frequently does not receive client-sent messages. When testing locally with a self-hosted SignalR, we never have any issues.

What we want to achieve is the following:

• Whenever a users opens a 'case'-page, we want to add that user to this specific case group.
• In the front-end (React) we do the following:

// When the 'Case'-page gets rendered

useEffect(() => {
  if (caseId && currentTeam?.id) {
    dispatch(joinCaseGroup(caseId, currentTeam.id));
  }

  return () => {
    const cleanup = () => {
      dispatch(leaveCaseGroup(caseId));
    };
    cleanup();
  };
}, [caseId, currentTeam.id, dispatch]);

// Function triggered by `joinCaseGroup`
connection.invoke('JoinCaseGroup', caseId, teamId))

• This gets handled in our Hub:

public class EventsClientHub : Hub
{
    /// <summary>
    /// Contains all the users that are in a case group
    /// </summary>
    private static readonly Dictionary<Guid, List<string>> UserCaseGroups = new();

    public async Task JoinCaseGroup(string caseId, string team)
    {
        // Here we check if the team has access to the case
        if (Guid.TryParse(caseId, out var parsedCaseId) && Guid.TryParse(team, out var teamId) && await _caseQueryHandler.TeamHasAccessToCase(teamId, parsedCaseId))
        { 
            // Remove from previous case groups, because a user can only be in 1 case group
            await RemoveUserFromCaseGroups();

            await AddUserToCaseGroup(parsedCaseId);
        }
    }

    private async Task AddUserToCaseGroup(Guid caseId)
    {
        // Keep track of all users in a case
        string userId = Context.User!.FindFirst("sub")!.Value;
        if (!UserCaseGroups.ContainsKey(caseId))
        {
            UserCaseGroups.TryAdd(caseId, new List<string>());
        }
        UserCaseGroups[caseId].Add(userId);

        // Add the user to the case group
        await Groups.AddToGroupAsync(Context.ConnectionId, $"case_{caseId}");
    }
}

Now, when debugging this, we see that the client does send the request and gets a response:

But when we check the live trace logs on Azure, we only see that the user gets added to his team group, but not to the case group:

The weird thing is, when we refresh a couple of times, the user sometimes does get added to the group and can receive live updates.

Any idea what the issue could be here?

Thanks in advance!