Thank you very much Charaf and Timmse for your help in locating the source of this issue and finally fixing it.
I am leaving here some more details in case someone else encounters te same issue in the future:
I am using runcloud to manage my wordpress installations. I was using Filezilla to access the server folders and create new files ( the custom elements). The issue seems to be I was logged in to root user, which even though the file permissions would be right, for some reason because they were created by root user then Bricks (wordpress installation is made through a different user, such as default runcloud user) would not be able to access these files.
The trick is to login to the correct user that you used for that wordpress installation (by default on runcloud it is “runcloud” user) and make the changes through that user. My mistake is I was logged in through “root”.