Connecting USB shielding of two hosts and one peripheral
My personal experience is that bonding the shield at two sides causes the USB not to work. I was in a hurry of connecting  Picoscope with no space inside a box and made a new cable with a 90 degree USB connector. My zeal of EMC addicted suggested me to bond the shield at both ends to the connectors shell (without a second thought...): damn to me, it did not work. Always in a hurry, I checked what is done in other cables that work and it was not connected: so quick and dirty, dismounted the newly made connector and removed the solder ball that I put there with a lot of effort.
With many equipment, possibly supplied from different sources, you would create a wonderful ground loop, ad this would have stopped me: but the Picoscope is fed from the same computer, so I thought that was not an issue.