Transfer speeds to USB micro-SD card drop after 3-5 copies
 

I'm running Ubuntu 14.04 on an intel 3370K (don't know if other hardwre info is needed) and when I plug a USB adapter for micro-SD card into my system and copy via Dolphin, it seems to copy very quickly (100MBps) for maybe 2-6 GB of data (usually 2-6 files) and then it often drops down to 50-300KBps. The card is a 32GB card with 80% free space, unfragmented.

If I close Dolphin, remove USB adapter, open dolphin & insert adapter again, i get good speeds for a few more copies and then it seems to start again.

Does this problem sound familiar to anyone or do you know what may be causing it?

I have tried multiple cards and adapters and it will do the same with tablets and smart phones, and different USB ports on the computer. Any ideas here?

How old are the SD cards?