I RMA'd a 1700x from 1707 and got a 1737 in return. No segfaults on the new cpu.
Also, who still hasn't RMA'd their CPU yet, if you plan to do so - it really speeds up the process if you have taken pictures of your BIOS settings in stock settings and overclocked, also pictures or screenshots of the faults in Linux. Photo of inside of your computer. Add as many information in the first e-mail as possible. I've read posts of people who say that tech support is making them do all these things anyway, so by doing it beforehand, you will save a good 2-3 days of waiting and e-mail exchange.
Overall i am very satisfied how the RMA process is being done.