I am curious if you are in any way associated with this project.
No I am not associated with them in away way, but I am following the project for a while and I was testing to see how it works in testnet, and I did noticed some bugs.
I didn't see many crypto projects that always have updated documentation, and Mercury was still in testing phase until recently so you can't expect miracles from them.
You could always ask them for feedback or write an issue on their github.
I think the other issues are probably more important to be addressed before anyone should consider trusting their money with this type of service.
I don't have to trust them, but they are just one of the layer two solutions for Bitcoin, and I could also say that I don't fully trust Lightning Network or Liquid.
Idea in Mercury is that you have full custody of your coins at all times, and you could always withdraw coins to regular Bitcoin wallet.