I understand your frustration.
all options and resources (may) fully utilize to fix the problem but the problem still occurred.
What I saying is give a last chance to the seller to honor the warranty claim.
If fail again then only lodge a dispute to tribunal court.
Don't worry, you can file in the courier charges as well to claim back from the seller (it is up to the judge). I have high confidence the judge will side with you and put a judgement to the seller to refund you + the courier charges.

The only risk I want to warn you is don't waste the judge precious time when the date court date is set and you tell different story to the judge. Straight to the claim you want refund for the product not working to your expectation. (FULL STOP). no but here but there.
You have all the evidence that all communication and warranty claim have been done with the seller but the issue is not solve. Based on this evidence you conclude you receive a defective product. (FULL STOP).

Nowdays I heard the tribunal cases has been concluded in fast and short period. Not like when it started, alot of backlog case.
Even my brother-in-law case within 2weeks being call in after the case being lodge. The judge immediate sentence the car washing company fault for damaging the engine during the car cleaning process. It cost him few thousand to fix the engine and the judge slapped the car washing company full price of the repair cost.