I created the free membership level set to 0.00. If all the fields get filled out and a template chosen when you click reserve your site it errors out and unchecks the terms of service like they weren't selected which they were. Is this a bug?
I reserved a test site using wpmutest username. I selected a template, filled out all fields, checked TOS and clicked on register my site. It registered smoothly without any error and resetting an fields.
If the issue still there, can you provide steps to replicate this issue on your website or on our sandbox/test sites.