Noticing with this last update that the stereo panners on the lower and main mixers have an annoying lag to them.
Not as smooth as they once were.
I just checked on my Windows 8.1 system and sure enough the latest 9.5.20 update adds a laggy latency when grabbing the stereo pans there as well.
I also reverted back to Cubase Pro 9.5.10 on my Mac and the issue is gone.
So this is a real issue.
Please look into this.
So now I’ve tested this problem on Mountain Lion.
The results are the same. Upon first grab of the stereo panner there is a bad lag which isn’t present in Cubase 9.5.10.
I just made a post now regarding the movement of a midi note. It also has that bad lag when you first try to move it. I’m pretty sure this must be related somehow.
Confirmed for the midi notes also. I also found that when having lots of audio edits (multitrack drum quantize) moving of crossfades becomes laggy and sticky as hell. As far as GUI is concerned 9.5.20 is a step back Im afraid.
Now that this was mentioned I notice the weird pan behavior. And, I agree that many things seem to have a newly introduced laggy feel about them too. Blah. 
But, with so many recent OS, driver and software updates happening, I find it amazing that any of this stuff works together at all. 
Regards 
Ive notices that this update brought back smoothing/aliasing- it can be noticed on the spectrum meters (9.5 and 9.5.1 have more raw lines on the spectrum meters than 9.5.20). Maybe this is one of the causes.
I went bak to 9.5.1 for the time being. However the mixer undo doesnt work. 
Hopefully it will get fixed in the next update.
Interesting observation Janko!
I went back to 9.5.10 as well.
Please investigate this issue Steinberg 
Still present in 9.5.21 update.
Still present in 9.5.30 update