Card Deck freezes on 2017 iMac

I’m trying to play games from OSG, namely La Patrie en Danger and other games of the series on my 2017 iMac. When I open the card deck button, I get a card deck display, but it is immediately frozen, and it also opens a frozen blank window next to it. Frozen = I cannot close it; I cannot deal a card from the deck; I cannot access the right-click menu. I have to Force Quit the game to get Vassal unfrozen, but I can never get the decks to work.

I also have a parallels desktop on the iMac, running Windows 10, and Vassal for Windows runs the OSG games perfectly, although with a different look to the interface because it’s Vassal for Windows.

I also own a Macbook. Using the same version of Vassal for mac, the same games, the same mac OS, but on my Macbook instead of my iMac, everything runs normally. There are no freezes in the card deck; right click reveals a choice menu allowing you to name how many cards you want to deal into the playing area. And you can drag them onto the playing area and view manipulate them normally.

My iMac might have a damaged OS or some piece of garbage from a Java-related virus or malware that may have migrated from a previous iMac (from 2011) and corrupted the 2017 iMac… If anybody knows how to straighten things out, I’d like to know about it. I have already run through the repair of all the disks. It improved performance, but the problem with (I suspect) Java and Vassal is unchanged.

With what versions of VASSAL and MacOS are you seeing this?