There is such problem in my Cubase Artist 9.5.
I try to input 64th notes to the midi track and set Quantize presets to 1/64. But when i try to input the note (i.e. pressing ALT and clicking the mouse) it’s input length is 1/32 instead. Can do nothing with that. This problem appeared only last week with new tracks, all my previous projects didn’t have such problem.
Up to where you have Snap ON/OFF, GRID, then you may have Grid Type to the right of that, make sure that is set to quantize and not Adaptive zoom
*IF you have that available in 9 or 9.5
It would help to see your computer specs, Cubase version, interface and that kinda stuff in your signature like mine. Click your User name top right then User Control Panel/Profile/Edit Signature