FTPS problem with small files

[#1]

Been transferring some files with FTPS single connection (3-50 MB)  normally  get speeds of 3000+ KB/s but in the last month every few files drops to less than 75 KB/s

If I cancel and restart file ( without disconnecting ) it goes back to 3000+ KB/s

Tried

Different  PC

Different Client

Different FTP server

Rebooting router ( moved gate ways from pcn-bng02 to pcn-bng04 )

Is this linked the problems that others have been posting about here ?

Speed tests come back as

http://www.thinkbroadband.com/speedtest/button/1483383479770544455.png

But Youtube now buffers some times,

And my son has issues with COD

[#2]

could well be, so far not found many other test cases to prove against, put small ftp downloads could be one to add into the test list.

[#3]

What host are you transferring files from if you don't mind me asking?

[#4]

Some network protocols can be horribly inefficient when transferring small files. SMB (the Windows protocol) is one such example - the difference can be quite startling. A hundred 100kB files will take several seconds to transfer. A single 10,000kB file will transfer in fractions of a second.

At a previous job where we were often transferring data from our office to the corporate servers in Minneapolis over a VPN we got into the habit of zipping the files first then transferring the archive. Even with the overhead of zipping/unzipping it was still faster.

https://forums.freenas.org/index.php?threads/slow-cifs-performance-small-files.42990/

[#5]

It has worked flawlessly since I joined in 2014 until Nov/Dec 2016

file size is 3-50 MB example

6.29 MB in 1 minute 27 seconds (73.6 KB/s)

Delete file and retry

6.29 MB in 2.38 seconds (3,378.8 KB/s)

I have ignored below 3MB as the transfer is too fast ( the hand shake takes longer )

the 3000 KB/s will be the limit of the server

I cannot reproduce with same file downloaded over and over , it has to be a queue