There were times when I noticed that a particular seller's always ends an auctions a few minutes to auction end time and cancel off all the bids. After many similar incidents, it aroused my suspicion.
After checking on the seller's transaction history for the past 2 weeks, I realised that the seller often did this.
In addition, there are a few bidders who only bid for this particular seller's items.
Thus I now completely boycott this seller.