Laggy file, freezing

Project is here:

It’s very, very odd. I keep getting all sorts of strange beaming (entire bars beamed together). And Dorico keeps freezing.

This piano part was recorded using real-time MIDI input. I also used Edit Duration–Fill to Next Note throughout the flow.

Is it perhaps because there’s a large amount of MIDI performance data contained in the flow, since the entire flow has preserved note durations?

Ugh, and I somehow lost the last 2/3 of the piano part.

I’m not in a position to look at the project file until I’m back in the office, but I think it’s unlikely that the midi data from the note velocities would have any impact on performance.