MAYBE

Proof:
ConCon could not decide confluence of the system.
\cite{ALS94}, Theorem 4.1 does not apply.
\cite{A14}, Theorem 11.5.9 does not apply.
\cite{O02}, p. 214, Proposition 7.2.50 does not apply.
System R transformed to optimized U(R).
Call external tool:
ttt2 - trs 30
Input:
  ?1(b, x) -> c
  f(x) -> ?1(a, x)
  g(x, x) -> g(f(a), f(b))

The external tool could not decide termination.
\cite{O02}, p. 214, Proposition 7.2.50 does not apply.
System R transformed to U(R).
Call external tool:
ttt2 - trs 30
Input:
  ?1(b, x) -> c
  f(x) -> ?1(a, x)
  g(x, x) -> g(f(a), f(b))

The external tool could not decide termination.