Transfer Speeds Crashed Recently - Ultra slow

[commandantp]

Hi!
First of, thank you for this amazing software! I'm in the donation edition because it is such a great tool. So thanks!

Now the Problem: I've been using the tool for years now. Lately copying files has been extremely slow but when I use the finderto drag and drop it is much faster [Mac OS Mojave 10.14.3, MBP i7 cpu].
Transfer rates at ~6MB/s with FreeFileSync instead to the 90+. See screenshot.

What I tried: I tried adding parallel thread operations (2 or 3) to see if it makes anything faster but it doesn't.

What I transfer and where: videos and FinalCutPro libraries. Large video files (3,4,6Gb) drop the transfer rates drastically and increase the CPU usage to 78% up to 99%. Looks the same for folders containing many small files.
I copy from one HD drive 5200rpm 4Tb to another HD Drive 7200rpm 10Tb.

I'd love to have your suggestions to improve the speed again.

Last question: in the help section about parallel threads, I haven't understood what the "optimal" is. Is it to put several threads at once on both drives? What are reasonable limits? Are SSD able to handle more threads than HDD?

Thank you so much for your help!

[MoD666]

Have the same, since updating to 10.14
Even a rollback to 10.13 did no change anymore.

My files are copying with around 5MB.

Let's see who has a clue.

Thanks for help everybody.

Cheers Julian

[MoD666]

Ok, I tried several things and in my case Speed is up again.

In my case the problem seems solved after changing the drive letters from A and B to M and L.
Seems like windows might be reducing speed in case of it things it would be a floppy drive.

And I completely deleted the current version 10.14 and installed 10.10.

Don't know which of both made the change, but that worked for me. Maybe try it as well.

[commandantp]

Thanks Julian! I'm on Mac so not sure if this will apply. I can try to roll back and see what happens though...

@Zenju can you get back to us please? Thanks