As an update, the multisensor did drop after 14 days or so. However, after doing some investigation using FAQ: Mapping your ZigBee network with Digi's XCTU - I realized that the garage sensor is only able to mesh with 1 zigbee device (poorly at that) on my network to get back to the samsung hub.
So I’ll probably just add some random sensor in the garage to give it another device to mesh/bounce off.