OnOff Shim not powering down correctly with rotary encoder on 3v3

I just installed the OnOff Shim on a setup where 3v3 is used by a hifiberry miniamp AND a rotary encoder like this one.

OnOff Shim shuts down as intended if the rotary encoder is not connected to 3v3.
But as soon as i connect the rotary encoder to 3v3 the Shim wont shutdown as expected: raspberry gets the shutdown command (and shuts down) but lights/leds don’t go out and i can’t restart the Raspberry via OnOff shim.

The hifiberry miniamp is also connected to 3v3 and makes no problem.
Any ideas how i could solve this problem?