This is a known issue at least with the Pi- it’s had a long history of pulling power from powered USB hubs. The interaction between this fact, and the On/Off Shim, however, is new to me.
At this point, I’d splice open a spare USB cable and snip the +5v line, making sure to strip it back somewhat and insulate the result. The link between the Pi and hub only needs Data+, Data- and GND and your hub nor Pi shouldn’t care that there’s no +5v connection between the two.
I’m not in the office to test if this cable cuts the data lines (that would seem odd to me) but you could also try using this just permanently in its off position: