We're sorry for any inconveniences caused, the reason this is happening is; you may be creating items within a list(s) you had prior to the upgrade. What you'll need to do is swipe left on the list in question and select "edit" then choose "due date". You'll then need to select "App Default" or a date of your choosing for the due date; this will allow the list to use which ever due date you've selected in settings.
List created in the new version of Todo will automatically be applied the default date you've chosen within settings
I just sent a message to support before I saw this thread. This is happening to me too (depending on what list I am in while creating the task). I have been using this app for quite a while now. I have always used a Focus list. Prior to the update if you created a task in the Focus list it would default to the Inbox. I would then have to manually move the task to the list I wanted. It looks as though the update behaves differently. I have my default list set to Home (list) and Today. When I am in the Home list and create a task I have no opportunity to access the Details and that newly created task has no date and gets dumped into "Someday".Interestingly, if I create the task in the Focus list it is assigned to the Home list and I have access to the details while creating the task. I think I have solved my problem, but am seeing some of the behavior as stated above depending on what list I am in.