I recently had a vendor deny a refund by the terms of their return policy. However, the terms they referenced were added after the purchase was made.
I was able to get a refund, but only after opening a claim with PayPal, and PayPal having to make a decision to issue the refund.
Some advice to protect yourself: use PayPal, read and save policies, and take screenshots of all communication.
Since my case is now resolved, I’m not going to name the vendor. Given the vendor’s good reputation, I don’t think they’re malicious. However, they may have just made a series of bad decisions.