Hi @Amy Cox ,
Sorry to hear you are having issues with our due dates.
I've tried to reproduce your issue here but did not manage to get it. In order to help you further, please submit a ticket here - https://trello.com/contact
I encourage you to submit some screenshots and with our internal ticket system, you have the option to give us permission to impersonate your account, which helps a lot.
We are waiting for your contact!
All the best,
Atlassian Support - Trello