Closing midi edit window causes playback glitch

This has started happening recently, but was not an issue with earlier interactions of Cubase.

Repro -

Create an Instrument track with any vsti, but Groove Agent will do for this.
Create a midi part - a basic drum beat is good for this.
Start Playback.
Open the midi editing window - playback continues perfectly.
Close the midi editing window - playback of this particular track will glitch.

In an arrangement with lots of tracks, playback is fine on all other tracks - its only the track whose midi editing window you are closing that now glitches.

Actually, the problem may just be closing the edit window on Groove Agent.

Update - no it’s not - it happens with various VSTi

I have this prob, I actually fixed it once but forgot what I did, if I manage to fix it again I’ll post it here.
I have it, closing windows, opening moving tracks can cause the glitch, specially when running in a loop and ya need to keep sync for online stream or jamtaba.

Seems VST guard has an impact with causing this glitch. I wonder if running cubase 8.5 as admin would solve it, but cubase won’t drag and drop proper when running as admin.