I have been getting this error for over 10 min when trying adding users to a PT project.
It is always followed by a message implying bad character input, but I have verified what has been typed.
I suspect the second error, is due to mishandling of the first error.
I have 11 people to add to 30-40 projects, but am not able to make progress due to this "Too many requests" error.
After ~15 min it worked for 3-5 min, now it has stopped for over 10 min again. It feels like this message is keeping me from even getting in the queue to have the request handled. Some might have prefer to come back tomorrow., but if I have many requests that need to be done soon, having the option to enter the queue would be very helpful.