YES

Problem:
 g(f(a())) -> f(g(f(a())))
 g(f(a())) -> f(f(a()))
 f(f(a())) -> f(a())

Proof:
 Uncurry Processor:
  f3(g(),f3(f(),a())) -> f3(f(),f3(g(),f3(f(),a())))
  f3(g(),f3(f(),a())) -> f3(f(),f3(f(),a()))
  f3(f(),f3(f(),a())) -> f3(f(),a())
  Ground Confluence Processor:
   confluent by decision procedure.