I’ve experienced the same issue. What you’re seeing is the throttling that Blizzard implemented in mid-may to try to mitigate the amount of network traffic generated by threat addons.
Since they didn’t have a means to reliably pull real time threat data about other raid members, they needed to communicate a large amount of data. Because of this, Blizzard enforced throttling and then in 1.13.5 they added the Threat API [source].
Unfortunately, they never withdrew the throttling.
From observing throttled behaviour, I can confirm the following:
- It is intermittent. It does not occur at the same time every day, nor does it necessarily occur every day.
- It is not occurring on all realms. I’m on Remulos-US and I’ve only experienced throttling a few times.
- C_ChatInfo.SendAddonMessage has a return value - whether or not the message was successfully sent. During periods of throttling, this will return true regardless of whether or not it is being throttled.
- Recent changes to my code suggest that the whisper channel may not be throttled. I haven’t experienced any issues with using that channel.
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- A quick note on this point - I don’t know how the backend of the messaging system operates, but the fact that I’m considering sending 40 messages via the whisper channel as opposed to 1 message via the raid channel… I’m lost for words.
Unfortunately, at this stage I can’t offer you a solution. I’m still trying to arrive at one myself. I only offer what I know and hope that it might be able to help you.