I would probably try to quit MC on the mini. Then restart it and before you do anything else, try to open the Options dialog. If that still doesn't work, I would recommend trying a different remote access system. Team Viewer is extremely sophisticated, reliable, fast, and configurable. It's free for personal use. The paid version is SUPER expensive, but personal use doesn't require a license.
There are also several VNC variants available, but (as I understand it) OSX "screen sharing" is actually using VNC under the covers. So using a different VNC server/client may or may not be helpful. I'd try Team Viewer.
It's an odd problem. I'll be interested to hear what you find. Good luck!
Brian.