Assignments/tables are showing as occupied for an hour or more as soon as they are seated

Sounds like a time zone setting is off either in your Waitlist Me account or one of your devices. On the website, you can go to Account > Settings to check the time zone for your Waitlist Me account. If that is correct, you'll want to check the settings in each of your devices themselves. 

Apple devices specifically come set with a time zone for PST. Go to Settings > General > Date & Time > Time Zone to check that it's set to your local time zone. Android users can check in a similar way by going to Settings > System > Date & Time.