Pressure Cook Oxtails: Add ¼ cup (63ml) balsamic vinegar, 1.5 tbsp (22.5ml) regular soy sauce, and 1 tbsp (15ml) fish sauce in Instant Pot. Carefully add browned oxtails in Instant Pot. Ensure they are partially submerged in the liquid. Then, layer the carrots and potatoes on top.
With Venting Knob in Venting Position, close the lid, then turn Venting Knob to Sealing Position. Pressure Cook at High Pressure for 40 minutes + Natural Release 20 minutes.
After 20 minutes, release the remaining pressure by turning Venting Knob to Venting Position. When Floating Valve drops, open the lid carefully.