Quantize bug:
Hitting quantize moves some notes way off. See Video
Mix Console bug:
Tracks are permanently greyed/ selected in Mix console. See video
Your video is unavailable. Turn it to Public instead of Private.
The link should work now. 
Good video. Clearly demonstrates the problem!
Shuttle transport is still broken with race conditions.
be interesting to see if anyone of these carried over, I don’t have 10.5 yet
https://www.steinberg.net/forums/viewtopic.php?f=283&t=171615
VST Connections window - label text (and general colour) has ‘whited-out’ in this update:-
Undo History Bug:
As you can see in the first video Cubase 10 Undoes edits made to the Flute part. Regardless of where in the history they were made.
In the second video you can see that Cubase 10.5 undoes edits made to the English Horn part. Even though the Flute part is currently active in the editor.
There is nothing in the manual about this behaviour.
En Cubase 10.5 no se mantienen las “Preferencias”