What I have found is that if you use a transmute preservation stone, you are pretty much guaranteed to fail.
If you don't use a pres stone, I found it always worked. An insane thing to try when you are trying to transmute an epic or upgrade onto your Arrendal. But I am just nuts enough to have tried (2 fails with pres stones, last time without worked) and wound up with an 'Epic' Arrendal.