Thanks for following up on this issue! I apologize that this has not been resolved as I know it's important for you to be able to post your campaigns to twitter to reach your customers. I did reach out to our technical support and they have advised me that this is a known intermittent issue with twitter and social share.
You response has been tracked and you will be provided an update when there is one. As a workaround in the meantime when you receive errors, you can copy the email link once it's been sent and manually post it on Twitter.
Hope this helps!
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