Date Fields lock after first signature in multi-signature PDF

Hello - 

I have a PDF form that, after the first e-signature and date, prevents subsequent users from using the dropdown date fields. I have made sure the fields are not locked and not read-only, but the problem persists. 

1. First person signs form, uses drop down calendar to select date, and saves and forwards the form to the next user.
2. The next user is able to drop an e-signature but the drop down calendar box is no longer functional. 

I have tried multiple different settings and troubleshooting steps and this has become quite frustrating. Any help would be appreciated.

Thanks!