Often, but not always, after messing around with solar panels in some capacity in the designer, it becomes impossible to leave the designer or save my craft. Trying to launch the vehicle simply closes the launch selection screen, the button to save simply does not respond, and the "Exit Designer" button also doesn't do anything. Annoyingly, the "Report a Bug" button also stops working, so I'm writing this report after restarting the game, which seems to be the only way to escape. This has happened more times than I can count. At first I thought it just happened randomly, but over time i started to notice that it seems to happen after I interact with retractable solar panels in some fashion.
Edit:
as soon as I posted this, I saved my craft, tried to set the solar panels on the craft shown to start closed, and was then was hit with the bug. I'm playing on windows 10 in fullscreen with a second monitor if that helps.