Hello. I apologize if this question has too many open-ends. I've been trying to put a box around the potential root causes, but so far I can't really narrow anything down.
I have an LG V10 with Android 6.0 on AT&T. When group messaging with iPhone users (some I know are also on AT&T, including my wife) and there's a rapid series of responses, I will experience delays in receiving messages. It looks like at a certain level of message throughput, message delivery gets throttled to one per minute. This can lead to significant delays, as you can imagine (I've gotten messages 20+ minutes after they've been sent, slowly, painfully receiving one message every minute). If I look at the timestamps in Textra, I can see clear evidence of this lag between the reported sent and received times (attached)
I've gone through every system, messaging and Textra-specific setting I can think of without any luck. I'm not even sure if this is an AT&T issue, an iMessage server issue, an LG issue or an Android configuration issue. I'm also not 100% sure that it's strictly an iMessage or even a group messaging issue, but I've only noticed it when group messaging with known iPhone users (which may be a false positive, since I may not have the same long-running, high-volume messaging sessions with android-only groups or single-correspondents).
I CAN confirm that when the problem becomes noticeable, I can see it impacting other concurrent messaging sessions as well. For example...
* iMessage group member sends a message.
* Multiple other group members respond.
* I begin noticing delays, and the delays mount as the messages queue up.
* Another iPhone user sends me a message 1-on-1 in a separate thread. THIS message is also subject to the queuing/delays.
I can't imagine this is some kind of typical throttling of messages through iMessage servers out into general SMS, as I would suspect tons and tons of folks would be complaining. I see plenty of complaints about delayed messages, but not with the same characteristics (the apparently 1-message-per-minute throttling, iPhone membership, etc). Again, these could be red herrings, but it all the evidence I've been able to compile so far.
Any advice, insight or encouragement is appreciated. Thanks!