I've been pulling my hair out for the past couple of days with Upfront/Spirit and responsive element positioning. I've finally figured out the issue and it would appear to be a reproducible bug.
I have been adjusting the settings in "Responsive Mode"to properly align and reposition elements for the various sized screens (Desktop, Big tablet, Tablet and Phone). The original layout for the page I'm working on was done and looked fine - but - when the screen size was adjusted, the elements on the page repositioned in a way that killed the flow of the page.
For example, two columns side by each left and right would reposition with the right side column above the left side, when viewed in a smaller screen. The associated images would also move around and the order did not seem to make sense. To resolve this - I used "Responsive Mode" and painstakingly adjusted the locations of all the elements in the page to accommodate for the smaller sized screen. I adjusted each of these for each sized screen (no fun). I then saved and exited upfront.
Later, if I noticed some element that needed to be tweaked in position for a particular screen, I would renter Responsive mode, make the adjustment, save and exit. BUT upon viewing the page on the various screens I saw that the elements were all out of position again. All my work had disappeared and the only change that was retained was the "tweak adjustment" I had made.
After a couple of passes readjusting elements for each and every sized screen - I finally realized that "Upfront" loses all the previous responsive adjustments whenever you re-enter responsive mode.
THUS - you only have one pass to make and save the adjustments to element positioning in Responsive Mode - Re-enter and you will need to start from scratch. (I dare not make any further adjustments to the project I was working on – or I'm back to the start).
I've enjoyed testing out Upfront/Spirit and really like the concept - but - until some of these issues are fixed, I'm going to have to steer clear - it's just too time consuming.