Since R15, if you try to edit a lightning component in an SFDX project, the lightning previewer just shows up blank without letting us resize it or collapse it.
Also, turning the Presentation -> Collapse Lightning Previewer option On or Off doesnt change anything, worse than that, trying to change the value of that setting while an SFDX project is open simply crash welkin.
Happens on multiple computer with brand new projects.
Reproduction video :