Comment 5 for bug 1907252

A fuller explanation is that "octet sequence cannot be decoded" stems from misuse of our foreign API internals via the normal publicly accessible API. It attempts to perform UTF-8 decoding on a string that got moved and the old bytes contain junk.
Why only x86 croaks has so far has been elusive. In theory, it should be a problem for all architectures.
So - note to self - this seems a moderately important issue to solve.