Can you make sure that you closed Duplicacy before reinstalling it? Otherwise you would be still running the previous instance. I’m pretty sure the bug that caused the kill signal not to be reported had been fixed. Running from the command line would be a better option.
If you can find a log line saying ‘Discarding file attributes’ then you’re running the latest build.
Also, if you’re limiting the upload speed to 7500KB/s then perhaps 4 or 8 threads are enough. In my tests a single thread is capable of uploading at 2MB/s at least.