You are running a very old DbVisualizer version. Are you also using Java 7? You can tell which Java version is used in the Help->About dialog in DbVisualizer.
I suggest you download DbVisualizer 10.0 with a bundled Java 8 VM and install it in a separate folder to test if this issue is related to old Java/DbVisualizer versions or something else.
This happens each time I close an open my latop lid. I have to force quit dbvis and start it again.
MAC OS 10.12.6
MacBook Pro (15-inch, 2017)
2.9 GHz Intel Core i7
16 GB 2133 MHz LPDDR3
Radeon Pro 560 4096 MB
Intel HD Graphics 630 1536 MB