frame drops with nvidia GSync

[ghost]

Hello, I get frame drops from 144 fps to 10-30 fps, if I use any programm coded in java while GSync is activated.
I tried it with JabRef and JOSM, its when the window is open and I do something there, like move it or hover my mouse over some icons so they get highlighted. When the window is open, but I dont touch it, I get no frame drops. When the window is in background (another noin java window is active) but visible, I can still hover my mouse over those icons and fps is stable (GSync uses with the other window then, I guess). When I disable GSync, then no framedrops aswell.

Windows 10 x64 1903
jre 8 update 221