"Your message could not be sent" - DM considered as spam




I am new here, I work for a company that developed a solution of live voting via twitter direct messages to a specific account.
To vote the direct message always has the same text: “Vote 01” or “Vote 02”…

During the competition, people that want to vote has a limit of 30 or 35 votes per day.
Now, it happened that after few votes, Twitter didn’t let people vote anymore providing the message in the object “Your message could not be sent”.
I guess Twitter could think of these DM as spam and it temporarly “ban” the account blocking the DM functionality.

We followed Twitter limits described in this page: https://support.twitter.com/articles/15364 is there a way we can fix it?

Thank you