It seems to work differently in the production release of Blender. When I select all of the faces, then press gg, it immediately selects the edges of all of the faces. But when I try to slide them, the results come out all wrong. It only works if I de-select the edges in between the faces. Then it works perfectly. I also got good results when I dissolved the three faces into a single face. It seems that it can’t handle multiple loops selected. Has anyone else tried it in the production version of 2.8 and been able to do it.
I think i had a few issues with this as well as it acted a little odd.
If you can upload your blend file i can take a look to see if it sparks in my memory what the issue was.
I have a feeling i had to do it slightly differently but i wont know until i can check the model over.