There seems to be a slight mismatch in the set of formulas accepted by jfs-smt2cxx versus jfs. An example is 20170501-Heizmann-UltimateAutomizer/cos_polynomial_true-unreach-call.c_9.smt2 (attached), which is quickly solved using jfs but dies with unsupported kind under jfs-smt2cxx:

user@ccbb42e224b5:~$ jfs/build/bin/jfs /out/20170501-Heizmann-UltimateAutomizer/cos_polynomial_true-unreach-call.c_9.smt2 
sat
user@ccbb42e224b5:~$ jfs/build/bin/jfs-smt2cxx /out/20170501-Heizmann-UltimateAutomizer/cos_polynomial_true-unreach-call.c_9.smt2 
unsupported kind
UNREACHABLE executed at /home/user/jfs/src/lib/Core/Z3ASTVisitor.cpp:237!
Aborted (core dumped)

I'll try to look into this more when I have some time but thought I'd file the issue in case it was instantly obvious what was going wrong.

cos_polynomial_true-unreach-call.c_9.txt