VSTs freeze the LMMS GUI (Linux+XEmbed, master)

I can load all of my VST instruments and effects without problems.
After loading they work as expected.
But all of them are freezing LMMS after minute or two. For example massTURBOtar and TAL NoiseMaker are free plugins that I have. Doesn't matter if 32 or 64 bit plugin.
This happens every time when VST window is visible and I click around.
If VST window is not open then LMMS may not freeze at all or it takes significally longer time to freeze.
During freeze there is no related console output that could hint about the problem even not in Valgrind.
Interesting that after LMMS main window and it's subwindows have frozen the VST stays usable. I can turn knobs etc and sound reacts to UI changes.
As a master branch user, I've had this issue for several months if not even longer.
Doesn't happen in 1.2 branch.
I'm using Manjaro Linux with Wine 4.2 from Manjaro repo.

Reproduce the freeze on Linux master with a VST window visible, clicking around after loading a plugin such as massTURBOtar or TAL NoiseMaker. Compare the behavior with the 1.2 branch; done means the LMMS GUI remains responsive while the VST window continues to work.