(set-option :solver.enforce_model_conversion true)
(declare-fun a () Real)
(declare-fun b () Real)
(assert (xor (>= b 0) (>= (+ (/ 5 b)) 2) (< a 0)))
(check-sat)
(assert (< (+ (* (- 6) a)) 4))
(check-sat)

[654] % z3debug small.smt2
sat
sat
[655] % z3 small.smt2
sat
unsat
[656] % 
[656] % cat small.smt2
(set-option :solver.enforce_model_conversion true)
(declare-fun a () Real)
(declare-fun b () Real)
(assert (xor (>= b 0) (>= (+ (/ 5 b)) 2) (< a 0)))
(check-sat)
(assert (< (+ (* (- 6) a)) 4))
(check-sat)