program gives different answer in Home and CAS

[roadrunner]

With the Function App active, this program:

PHP Code:

EXPORT TANGENT()
BEGIN
 LOCAL f, sf;
 "X^2-2*X+3"▶F1;
 EXPR("F"+1)▶f;
 diff(f,'X',1)▶sf;
 RETURN sf;
END; 


when run from Home returns the correct answer, 2*X-2. The same program when run from CAS returns 0. This is on the emulator running version 2.1.14592

Oddly enough on the handheld running version 2.1.14588 it works correctly in Home and CAS.

Can anyone tell me what is wrong?

-road