Crackling Audio on Bluetooth with Upstream Mini

I’m running an Upstream Mini paired with a TPA3118 amp board powered with a desktop 15V (80W) power brick. Voltage to the Upstream Mini is stepped down using a Step Down DC-DC converter

This is followed by a DC-to-DC isolator:

This works perfectly on WiFi. However, on Bluetooth , it gives out a slight crackling audio. I’m playing on both on Spotify & Tidal on OnePlus 8T, SBC encoding. I’ve tried using the on board BT antenna as well as attaching an external similar with what Arylic is using for WiFi.

Anybody had similar issues?