My friend also gets this problem and also on a “high end” Windows computer (oversized laptop in his case) and also has no issue on other machines. The problem recently seemed to go away; he was on Vassal v3.2.17 and is now on v3.3.2 but this probably isn’t what fixed it, if indeed it is fixed.
His post and another more recent one from someone else, seemingly same issue, along with developer’s take on it:
https://forum.vassalengine.org/t/screen-painting-issue/10746/1
https://forum.vassalengine.org/t/cannot-cope-with-vassal-multiple-windows-all-the-time/10459/1