I believe only very early silicon was affected. AMD replaced CPUs for people on request. If you google you can find the affected datecode visible on the CPU. I have an early Ryzen from the next date and it doesn't have any issues.
I've seen about a dozen reports of faulty post-week-25 processors crop up in the AMD Community Forum and on Reddit from different users. Which is of course a lot better than pre-week-25 where the overwhelming majority of units are faulty. Of course, most users aren't testing for it in the first place, especially since the newer processors were widely (and incorrectly) reported to be "fixed", so it's hard to say.
https://community.amd.com/thread/215773?start=1635&tstart=0 (user jcoiner, 1726PGT)
https://community.amd.com/thread/215773?start=1725&tstart=0 (user scorpio810, 2x 1728SUS)
https://community.amd.com/thread/215773?start=1770&tstart=0 (user ryzlin, 1733PGT)
https://community.amd.com/thread/215773?start=1785&tstart=0 (user flyinryzen1700, 1737SUS)
https://community.amd.com/thread/215773?start=1830&tstart=0 (user skimba 1725PGT, user xtronom 1728PGT)
https://community.amd.com/thread/215773?start=1860&tstart=0 (user jc_yang, 1742SUS)
https://community.amd.com/thread/215773?start=1875&tstart=0 (user fedor_s 1726SUS, user karabojkov 1741SUS+1737SUS, user spiffy 1748PGS)
https://www.reddit.com/r/Amd/comments/76q7ne/got_a_defective... (user grosbof 1733SUS)
https://www.reddit.com/r/Amd/comments/7ar15o/psa_amazon_is_s... (user triplesal, 1733PGS)
https://www.reddit.com/r/Amd/comments/7ar15o/psa_amazon_is_s... (user istockporno, 1726PGT)
I am guessing that this was finally squashed for good in the 2000-series stepping.
Incidentally, there have been reports of the latest patch of Battlefield One having strange random crashes on Ryzen 1000-series but not 2000-series or Intel processors, that is reportedly fixed by disabling SMT, and I'm wondering if that's another manifestation of the segfault bug. It's hard to say, and the reality is the first-gen silicon will never be 100% trustworthy. Buy 2000-series processors instead, it's worth it for the peace of mind.
How does one do the test?
https://github.com/suaefar/ryzen-test
There is also a Windows variant that may be more sensitive than the Linux variant but fewer people have used it so YMMV.