Listener Erroring on Arm from Custom List

I am trying to setup a listener on a series of tracks whose position may shift. When the listener is using a Custom List value, I receive critical error.

Doing some troubleshooting, this custom list value is populated correctly – If I remove the get list from the listener and instead put in a CSS log action block, it works correctly.

Attached JSON:

Mapping: INIT – Capture Track Locations builds the list (On a generic Ableton session, all values in list are 0)

Mapping: Testing Arm in Listener