Toucan 3.1.x never worked properly

The last version of Toucan that works "well" is v3.0.4.
I've tried every single release since then, and they are all much worse than 3.0.4.
The first 3.1 release had this annoying "feature" recording all the skipped file. This was eventually fixed. But another problem that was never fixed:
- I have a folder, with just below 9000 files to backup, from a SSD to a USB pen drive, with Toucan on the target pen drive.
- With v3.1.8.2, Toucan hogs the CPU, and after literally 30 minutes, still not finished (not sure where it's at), while the CPU fan is in overdrive. Trying to "Cancel" doesn't seem to respond even after waiting 30 seconds, so I have to kill Toucan from the task manager.
- Returned to Toucan v3.0.4, under the same conditions, folder done in under 3 minutes.

My backup options are:
Mirror.
File checks: size + short comparison.

Running Toucan 3.1.8.2, I fired up Process Monitor, and it does see Toucan doing some file access. But strangely, although I r4ecognise the files names very slowly scrolling, Process Monitor tells me it tries to access my files from within the Toucan folder? So if Toucan 3.1 tries to copy every single file or a subset thereof to its own folder before deciding if the file needs to be copied or not, that would explain why it takes forever.

Note that I tried to run a backup from a SSD to a SSD with Toucan 3.1.8.2, and that worked, although again I think it takes quite a while longer than with Toucan v3.0.4.