USB Flash drive speed query

I am having issues in recent days with copying files from a USB 3 drive to a flash drive in that the speed starts off fine then crashes to dead slow or zero then the speed picks up again. File sizes are small, typically from 500MB to 3GB.
I know this an old, O-L-D issue but am seeking the REAL cause not a fix.
I always use the context "send to" to copy files.
I tried it with Win Explorer instead and no problem!
I send files to Documents instead and again no problem.
I reversed it and sent from the flash drive to Documents. No problem.
The flash drive is a Sandisk Ultra 3.0 and I bought a brand new one just to see, and no cure.

So the question is - what is the problem when writing to flash drives? It smells of a caching issue more than anything but there's no configurability there as far as I know.




I don't know what Microsludge are doing. Why can't Send to and explorer copy work the same way!?
It's like the taskbar "safely remove hardware" which always has an issue with locked drives but eject every time via My Computer.
Admittedly Microsludge admit the safely remove hardware is deprecated and no longer being patched.

caching, connection type, file size and file system format all play a part.
most USB sticks are FAT32 you could try formatting them to NTFS.
and there are a few other things that can be checked.

best of luck, Steve ..

They are NTFS

More of a Windows developer question.
Maybe Dave's garage...