Hi Jim,
This sounds like another manifestation of this issue.
If so, it does indeed appear to be MacOS related and I trust it will be resolved by the upcoming workaround in Vassal 3.7.16 that I announced here.
Interested to hear if the workaround is ok for you. We were unable to find a way to restrict delete to the in-focus window, though that seems to be automatic on other platforms.
Mark