Copying From X2D SSD Very Slow on MacBook Air Is This a Cable Problem?

[pflower]

I have been travelling with my new X2D and an old MacBook Air - a 2.2 GHz Dual Core Intel i7 which only has USB 3.0.  It is fine for what I need.   But copying from the X2D is really slow.  For safety's sake I copy all files from the camera to the internal hard disk and then to an external Sandisk portable SSD (connected to the MacBook via USB). Approx 100 3FR files takes up to 10 minutes.  If I choose to copy them to the external SSD before the internal disk there is no difference in speed.  But what is really confusing me is that having, after 10 minutes, copied all the files to either the Sandisk or the internal hard drive, and I then try to copy the same files between the two the files just go in about one minute.  So what is going on?  The internal hard disk and the SSD are still communicating via USB 3.0.

Is this a cable problem?  I have used various USB C to USB A cables when transferring to the MacBook.  No difference.  But returning home I got out the supplied cable which, being USB C to USB C I couldn't use on the MacBook but I got it into my iMac which has USB 3.1 and the files transfer onto the internal disk quickly.

Any thoughts?

[boojum]

It is also slow using the HB cable to a Linux platform.  These are large files.  I shoot RAW and JPEG.  But it is not like this is hard work.  Just hook it up and let it go.