I just installed cubase 9 pro (from 7.5) and unfortunately I noticed a macro of mine isn’t working anymore…
Macro description: Delete all Keyswitches Under Selection (when in the key editor window)
Transport - Play from Selection Start
Edit - Select None
Transport - Stop
Transport - Nudge +1 Frame
Edit - Select Under Cursor
Process Logical Preset - Delete Selected Keyswitches (this one deletes all selected notes from C0 to B0)
The first thing I notice is that Play from Selection Start and Stop are not properly working in series.
You could try inserting a simple open transport panel and close again.
Greg Ondo does that in some of his videos, when there are timing problems (commands getting ignored)