Connected subchannel without notification

[TE-JoakimElvander]

Hi, I have run into an issue multiple times now, but have a hard time tracking it down since it seems to come from the grpc library and not from your code.
I see the message in the log "New connected subchannel at for ". Normally when this comes, I get a callback through the registered callbacks and create a client and start communicating. But sometimes I get no notification at all. The connection remains open (netstat reveals it to be established), but since I don't get the callback, nothing is done with the connection.
If I then restart the whole connection setup, the channel is kept alive and is established immediately (i.e. the underlying allocations remains) - and I get the notification that I may proceed and everything works again. I have no way of mitigating this as it's only visible in the log that the service has connected...
Do you have any idea what might be going on here, or if there are conditions where the callbacks won't fire when the service has connected?