slow sync since upgrading to FFS10.9

[rdewild]

I had a system backup running using FFS on a server 2008 using FFS v.7.2
This sync would take between 5 and 6 hours. The sync occurs over a VPN to a remote location

Last November, 2018 we upgraded our server to a Server 2016 64 bit.
The sync time slowed down to about 15 hours for the same folder pairs.

We recently upgraded to the "donation edition" of FFS to make use of the parallel file operations feature.
But, this did not make any difference in the sync time.

Looking for some tips on how to trouble shoot this drastic slow down between version 7.2 and 10.9
Thank you.