Quantize everything

After

You need to provide adequate details & context before folks can help you.

What function might you mean?

Since your initial problem was occurring in the Key Editor and this new problem based on your pics is apparently happening in the Project Window, it doesn’t seem like they could be the same problem. But again without any description or explanation it’s close to impossible to know what is happening.

The problem I have is that if I select all events, whether it is in the key editor or project window or wherever I need to make adjustments, using the timeline, all selected items/events snap to one position as depicted in the before and after screengrabs above. This does not happen if I select one note/event, to move, but, if I were to do this, it would be time consuming, so I select all to save time for bulk movements. Have checked if this problem of mine occurs in other versions of Cubase but it doesn’t (have checked versions 8, 10 and 11). I have compared all preference choices in the preference box and toolbar in version 12 against those in versions 10 and 11 and there are no differences.
I seem to remember a while back an announcement that this feature had been created, but at the time I opted not to use it because I thought the feature was crap and could see no use for it. And now it appears to be implemented as standard in one of the recent updates and I cannot turn it off.