I'm quickhashing a folder tree with 500K files.
The MD5 calculus and data output is OK and fast.
But when I copy to clipboard or save the spreadsheet to HTML or CSV, it takes an enormous amount of time (4 hours+).
The CSV file is ~ 50MB size when completed.
The first 5-10MB go fast (mins), but then it starts to get slower and slower until it crawls for several hours.
It does not depend on the target HDD, I tried exporting the data to SDD or HDD, same result.

Another side behaviour while doing this operation is the memory usage, the system has 16GB and QuickHash uses more and more to 10GB RAM.