First off, love the product. I’m not 100% sure this is due to Mosaico, but here is my scenario. I use outlook and will often open a second window of it for the Calendar. I then stored the arrangement with Mosaico. The issue comes when I restore the arrangement. One of the windows become “wonky”. It doesn’t get moved to the correct location and when I click it to drag, it immediately minimizes. I have to close the window through the taskbar and then reopen it. Sometimes even that doesn’t work and I have to close the entire application and restart it. In some cases even that doesn’t help.
A possible clue is that I’ve found the description below fixes the issue temporarily. If I go into RegEdit and find the folder HKEY_CURRENT_USER/SOFTWARE/Microsoft/Office/xx.yy/Outlook/Office Explorer and then delete the entry called Frame. I don’t know if that is somehow related to Mosaico, and like I said it may be caused by something else entirely, but I wanted to run it past you and see if you can tweak this part of the puzzle on what has otherwise been a great piece of software.