If it comes up you just have to wait a minute or so before posting again. Often just refreshing the page is enough. It can happen if a lot of people are posting at the same time too, it's not personal - just means the server is being asked to handle too much in one go I think.

thx but I did wait & couldnt post. & certainly couldnt do that to share an entire series.

Workaround?

From what I have heard, if this came up when you tried to post a picture, a workaround would be to also post some text with every picture. Maybe posts without any text are blocked, that would make sense.