TRD Sway bar rattle after new suspension install

[kobe52]

Hey y'all, I got a 09 Yaris sedan and just recently replaced the stock susp with TRD springs and tein struts/shocks. After install, I noticed a light shallow rattle sound in the rear over very shallow road bumps, sounds like the shaking a deck of cards in the box. Rechecked and retightened all the bolts. Emptied the trunk etc if it was item noise. Noise didn't go away.

When taking it for alignment I asked them to check the rear if they could find play while car was on the ramps. Apparently the sway bar has some play/flex and is rattling on the torsion beam.

Is there any suggested remedies?I've had the sway bar since 22' June. When I first installed it back then, it had the same noise, but it went away when I retightened one of the shock bolts. But now all 4 bolts seem pretty tight and to torque spec.

Maybe some sort of homemade dampener around the bar or somehow my stock shock bolts are backing off slightly(thread stretch?) and to either replace them or loctite/lock washer/nylocs?