Edit: The issue is not Retrologue related. Retrologue was chosen for testing purposes because most Cubase users have access to it. Any VST or external instrument can be use for tests as this is a general midi issue.
Steps to reproduce:
1/ Using a sine tool with 16th quantization value automate Retrologue’s filter cutoff VST parameter in the arranger window - sounds right, smooth and regular
2/ Cut the automation from the filter automation lane and paste it to MIDI CC 74 (Brightness) automation lane in the arranger window - this time Retrologue’s filter cutoff will be automated using MIDI CC automation - sounds off, not smooth and irregular
You can start with drawing MIDI CC automation and moving it to filter cutoff parameter automation - result is the same - vst parameter automation is smooth, MIDI CC Automation isn’t.
Drawing sine automation using 16th quantize value and 1/128 length quantize value in the MIDI EVENT, however, gives a smooth result. It is only MIDI CC automation in the arranger window that is broken.