The basic idea of making trading safer is good at first, the realization of it by them isn't thought through. Coins that were send can be eradicated even if the merchant is legit and they boldly clain that won't happen. Can't image any merchant accepting such payments. That concept is not great at all and there is little information in their whitepaper about anything. Honestly, the proof of concept is nonsense.
Welcome to the BTC Talk forum!
Could you elaborate about your problem with our proof of concept?
This would help us understand you better and offer a better product!
Your worry regarding transactions being invalidated without a good reason is mentioned in our FAQ, under point 8.
FAQ :
https://savact.com/menu/faq/We have also calculated potential losses from such cases in our proof of concept.