Don't you find weird that this address has already been used 6 times since October? I don't think you can be "100% sure" that this wasn't a mistake on your end.
I move coins for hours at a time daily. I opened browser, went to chipmixer.com. No typos. I can produce session IDs for 0.3 bitcoin for up to 2 hours before this funky one. No problems ever.
I'm telling you, I'm the last person to make a mistake like going to a wrong site or having copying and paste hijacked or whatever else there could be.
It's okay, I'm convinced I can't trust this site, I've already moved on. You guys be careful too.