Thank you for sharing that issue with us. I just tried to reproduce it but couldn't do so. First of all, I launched a fresh Bitnami instance in AWS with Mautic 2.15.0-0 and created a new contact. After that, I edited it and added a social profile
As you can see, there was not any "default" value in the social profile fields. I saved the profile and obtained the information of the user
I also checked the error_log file of Apache and didn't obtain any error message. Could you please let us know the Mautic version you are using?
We have a Support Tool that will gather relevant information for us. Could you please download and execute it on the machine where the stack is running by following the steps described in the guide below?
How to Run the Bitnami Support Tool
Please note that you need to paste the code outputted by the tool in your reply.