Quantizing a 16minute midi clip with lots of drum note data causes a GUI lock-up here. I just lost an entire 16minute jam. Not super thrilled. Can reproduce.
Can anyone else reproduce this???
Select the clip in the docked midi editor. Select all events. Hit Q to quantize.
Locks up.
Ah. Interestingly, if I only select notes and not the CC values, it doesn’t hang.
Why don’t you Quantize from BFD’s Groove Editor Track, Drew? It’s excellent! 
If there’s too many controller nodes, you can MIDI>Functions> Thin Out Data to bring them down to a more reasonable level.
Was it CC4 data that caused the mayhem? I want to give it a go!
Yep, think it was CC4.
Use the BFD groove editor??! I’d be the first person in the world to do that!! 