When you’re quantizing a part it’s the note data that gets moved around. If a part also contains control data like pitch bend, the note and control data can become detached which can make things sounds very strange.

In Cubase SX/SL 3.x controller data for a MIDI track can be quantized along with the corresponding MIDI notes in order to preserve their relative timing. Select your notes or events then navigate to MIDI Quantize Setup… and choose your basic quantization parameters. Check the box labeled ‘Move Controller’, and click the ‘Apply Quantize’ button to perform the action.