I did get it from an Amazon.ca third-party (but that particular seller is listed as an official reseller over at Icy Dock) and I have two more on the way. Maybe I’ll get lucky with the other units. At least I can send everything back to Amazon (since it was fulfilled by them) if not.
I’m tempted to disassemble the unit and check for PCB damage or cold solder joints around the connectors. Reflowing the solder would be an easy fix at least.
In the Rosewill RSV-L4500U they need to inserted upside down or it’s impossible to fit more than 2 (the last one is blocked by the power buttons/lights/usb ports section on the right). The slides can only be installed in one position on the dock, and the alignment on the case makes it impossible to use them in the usual orientation.
Thanks for your reply btw!