Thank you for all the information you provided, we tried to reproduce the issue following the information but we couldn't do it. This is what we did:
- Create a new folder inside the WordPress' htdocs folder
sudo mkdir testUploadFolder
sudo chown bitnami:daemon testUploadFolder
sudo chmod 775 testUploadFolder
As you can see, we created the folder inside the htdocs one and modified the permissions of it. Once created, we modified the wp-config.php file and include the following line above the "That's all, stop editing! Happy blogging." line.
define( 'UPLOADS', 'testUploadFolder');
Then we saved the file and accessed the application. We uploaded the Bitnami logo using the "Add New" button in the "Media" section and everything worked correctly.
As I mentioned, we used a fresh installation of WordPress and only modified the UPLOADS parameter, did you modify any other configuration file?