Game Bogs down with large window

iMac 27" late 2013
Vassal 3.2.16
Java 8

If I keep the window fairly small, Vassal runs more or less ok, but if I expand the window to cover the screen, it totally bogs down and becomes unusable.

Any ideas would be appreciated.

edit: actually it seems to be a function of how zoomed out the map is. Zoomed all the way out bogs the game down completely, zoomed all the way in works ok.

Update: This is the first module I’ve run since updating to Sierra, and up to now, I haven’t used Vassal a lot in general.

It looks like this issue is confined to one module, GMT 's Roads to Moscow. Having loaded a number of other modules and having them all run fine.

Looks like I’ll just have to deal with it for this one.