Pocketbook Touch HD - usb device not recognized

[Capricorn]

Ever since I put an SD card into my pocketbook touch HD I have had problems connecting the Touch HD to my computers.

Changing usb cables did not help.
Changing usb ports did not help.
Removing usb drivers in the device manager and reinstalling them did not help.
Other devices like a USB stick, like some external hard disks, like a mobile phone, all worked without problem on these same usb ports.

The only thing that sometimes helped, was reformatting the internal memory. But that too, often only worked for a short time or not at all.

I have had this problem on two very different machines, a 12-year old computer I built myself, and a HP Z440 which I bought second-hand this year.
On a third machine, a Lenovo C340, it usually worked, but it would often ask to repair my usb drive ie the Touch HD.

I have now found a solution to my problems: I have connected a usb hub (TP-Link USB 3.0 7-port, which has its own power supply) to my computer, and now I connect my Touch HD only to this usb hub. Result: No more problems.
Every time I connect the Touch HD, it is recognized properly and stays connected.
I can now transfer books from my Calibre database to my ebook reader, without losing the connection in the middle of a transfer.

I recon it is because the usb standard was never very well defined and therefore there are variations between the different USB producers that result in problems, when trying to connect.

I post this because it may help some people with similar problems.