UFD property for power series in characteristic 0

Question

Samuel famously produced an example of a UFD, namely $S = R_{(x,y,z)}$, where $R = K[x,y,z]/(x^2+y^3+z^7)$ and $K$ has characteristic 2, such that the power series extension $S[[ x ]]$ is not a UFD. While he gives a general method for constructing such examples, it doesn't seem to work easily in characteristic 0. So the question is: Are there any characteristic 0 UFDs $R$ such that $R[[x]]$ is not a UFD - preferably explicit ones?

Reference to Samuel's paper: On unique factorization domains.

Note: $S$ is a UFD in arbitrary characteristics by Nagata's criterion — see here: $(K[x,y,z]/(x^2+y^3+z^7))_{(x,y,z)}$ is a UFD.

Making $S[[x]]$ not a UFD is the tricky part.

Answer 1

For any field $k$, the ring $A = k(U)[[X,Y,Z]]/(X^2+X^3+UX^6)$ is a UFD such that $A[[T]]$ is not a UFD. For a proof of this, see

Salmon, Su un problema posto da P. Samuel.

For further developments, see the first two pages of

https://www.mathnet.ru/php/archive.phtml?wshow=paper&jrnid=sm&paperid=3365&option_lang=eng

(V. I. Danilov, On a conjecture of Samuel, Mathematics of the USSR- Sbornik, 1970, Volume 10, Issue 1, 127–137 DOI: 10.1070/SM1970v010n01ABEH001590)

as well as

Lipman, Unique factorization in complete local rings.