BUG? sometimes unsatisfiable

[manythanks]

posting your code:
% variables
var float: R; % quarterly repayment
var float: P; % principal initially borrowed
var 0.0 .. 10.0: I; % interest rate

P = 1000;
R = 260;
I = 0.04;
% intermediate variables
var float: B1; % balance after one quarter
var float: B2; % balance after two quarters
var float: B3; % balance after three quarters
var float: B4; % balance owing at end

constraint B1 = P * (1.0 + I) - R;
constraint B2 = B1 * (1.0 + I) - R;
constraint B3 = B2 * (1.0 + I) - R;
constraint B4 = B3 * (1.0 + I) - R;

solve satisfy;

output [
"Borrowing ", show_float(0, 2, P), " at ", show(I*100.0),
"% interest, and repaying ", show_float(0, 2, R),
"\nper quarter for 1 year leaves ", show_float(0, 2, B4), " owing\n"
];

gives me
Compiling LOAN_TUPOS_KATEBASA.mzn
Running LOAN_TUPOS_KATEBASA.mzn
=====UNSATISFIABLE=====
Finished in 1s 728msec

Running very similar commands
var float: p = 907.47; var float: r=200; % var 0.0..2.0:i;
var float: i = 0.04;
var float: b1;
var float: b2;
var float: b3;
var float: b4;
%intermiate variables
constraint b1 = p * (1 + i) - r;
constraint b2 = b1 * (1 + i) - r;
constraint b3 = b2 * (1 + i) - r;
constraint b4 = b3 * (1 + i) - r;
solve satisfy;
output ["P=(p) R=(r) I=(i) b1=(b1) b2=(b2) b3=(b3) B4=(b4)"];
I get the same result,

BUT if I run, some different numbers: (r=20 instead of 200)
I get the solution
Compiling simpleLoan1.mzn
Running simpleLoan1.mzn

P=907.47 R=20.0 I=0.04 b1=923.7688000000001 b2=940.719552 b3=958.34833408 B4=976.6822674432

Finished in 566msec

[manythanks]

what i have is

[manythanks]

Everything works fine, if I initially manually change to G12 MIP solver.